#sortings

CF 1388E - Uncle Bogdan and Projections

CF 1388E - Uncle Bogdan and Projections Rating: 2700 Tags: data structures, geometry, sortings Solve time: 1m 38s Verified: no Solution Problem Understanding We are given several horizontal line segments placed above the x-axis. Each segment has a fixed height and a horizontal interval with integer endpoints. The segments do not intersect each other in the plane, but they may lie at different heights and overlap in x-projection. We choose...

CF 1375D - Replace by MEX

CF 1375D - Replace by MEX Rating: 1900 Tags: brute force, constructive algorithms, sortings Solve time: 1m 24s Verified: no Solution Problem Understanding We are given several arrays, each containing integers in the range from zero up to the array length. We are allowed to repeatedly pick a position in the array and overwrite its value with the current MEX of the entire array. Since the MEX depends on the...

CF 1267I - Intriguing Selection

CF 1267I - Intriguing Selection Rating: 2600 Tags: brute force, constructive algorithms, implementation, interactive, sortings Solve time: 2m 16s Verified: no Solution Problem Understanding We are given a hidden set of $2n$ distinct values, one per player, and we can only compare two players at a time and learn which one is stronger. The goal is not to fully reconstruct the ranking, but to identify exactly which $n$ players belong...

CF 1256F - Equalizing Two Strings

CF 1256F - Equalizing Two Strings Rating: 2000 Tags: constructive algorithms, sortings, strings Solve time: 1m 25s Verified: no Solution Problem Understanding We are given two strings of equal length, and we are allowed to repeatedly perform a synchronized operation: pick a length len , choose any substring of that length in the first string, reverse it, and independently choose any substring of the same length in the second string...

CF 1253E - Antenna Coverage

CF 1253E - Antenna Coverage Rating: 2200 Tags: data structures, dp, greedy, sortings Solve time: 1m 54s Verified: no Solution Problem Understanding We are given a set of signal towers placed on a number line. Each tower has a fixed position and a symmetric coverage radius. A tower at position $x_i$ with radius $s_i$ covers every integer point from $x_i - s_i$ to $x_i + s_i$. The radius of each...

Kotlin Heroes: Episode 2

Kotlin Heroes: Episode 2 Kotlin | 9 problems | 6/9 verified | Difficulty 1000-3100 | 23m 44s # Problem Rating Tags Accepted Time ✓ A Three Problems 1000 *special, implementation 1,583 1m 42s B Traveling Around the Golden Ring of Berland 1500 *special, implementation 800 1m 38s ✓ C Ice Cream 1700 *special, greedy, sortings 567 1m 16s ✓ D Teams 2000 *special, binary-search, greedy 252 6m 33s ✓ E...

CF 1211C - Ice Cream

CF 1211C - Ice Cream Rating: 1700 Tags: *special, greedy, sortings Solve time: 1m 16s Verified: yes Solution Problem Understanding We are given a sequence of days, and on each day there is a price for buying a single ice cream portion. Each day also comes with constraints describing how many portions Tanya is allowed to eat on that day. Across the whole summer she must eat exactly $k$ portions...

CF 1167F - Scalar Queries

CF 1167F - Scalar Queries Rating: 2300 Tags: combinatorics, data structures, math, sortings Solve time: 1m 24s Verified: no Solution Problem Understanding We are given an array of distinct numbers, and we look at every possible contiguous subarray. For each subarray, we temporarily reorder its elements in increasing order, then assign weights based on position in that sorted subarray: the smallest element gets weight 1, the next gets weight 2,...

CF 1075B - Taxi drivers and Lyft

CF 1075B - Taxi drivers and Lyft Rating: 1200 Tags: implementation, sortings Solve time: 57s Verified: yes Solution Problem Understanding We are given a set of people positioned on a number line. Each person is either a rider or a taxi driver, and all positions are distinct and already sorted in increasing order. When a rider requests a taxi, the system always assigns the request to the closest taxi driver...

CF 958E2 - Guard Duty (medium) Rating: 2200 Tags: binary search, dp, greedy, sortings Model: gpt-5-3-mini Solve time: 3m 26s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a339e66-d274-83ec-9c8a-9aa9396149de Solution Problem Understanding We are given a strictly increasing sequence of time moments when Heidi temporarily leaves hyperspace. These moments are the only valid endpoints at which meetings can begin or end. Heidi must organize exactly $K$ disjoint meetings, where each meeting is defined...

CF 1038C - Gambling Rating: 1300 Tags: greedy, sortings Model: gpt-5-3-mini Solve time: 5m 32s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33b850-8950-83ec-9224-95747a804177 Solution Problem Understanding Two players each hold a multiset of integers. They take turns, starting with A. On a turn, a player either consumes one of their own remaining numbers, adding it to their score, or discards one number from the opponent’s collection, which does not affect score directly...

CF 990B - Micro-World Rating: 1200 Tags: greedy, sortings Model: gpt-5-3-mini Solve time: 1m 28s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33ab40-4628-83ec-b07d-d37d37181695 Solution Problem Understanding We are given a collection of bacteria, each with a fixed size. A larger bacterium can consume a smaller one only when two conditions hold at the moment of interaction: it must be strictly larger, and at the same time it cannot be too large compared...

CF 1042F - Leaf Sets Rating: 2400 Tags: data structures, dfs and similar, dsu, graphs, greedy, sortings, trees Model: gpt-5-5 Solve time: 1m 22s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33bd15-e528-83ec-b5a4-de0286e26609 Solution Problem Understanding We are given a tree where only some vertices matter: those with degree exactly one, which we call leaves. The task is not about grouping all vertices, but only about grouping these leaves. Each group must satisfy...

CF 991B - Getting an A Rating: 900 Tags: greedy, sortings Model: gpt-5-3-mini Solve time: 57s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a33abdb-0708-83ec-9dd2-80237283c7dd Solution Problem Understanding We are given a list of lab grades, each between 2 and 5. The course grade is computed as the arithmetic mean of all lab grades, then rounded to the nearest integer. The rounding rule is standard “round half up”, meaning values like 4.5 become...

CF 995C - Leaving the Bar Rating: 2300 Tags: brute force, data structures, geometry, greedy, math, sortings Model: gpt-5-3-mini Solve time: 1m 17s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a329559-3654-83ec-b447-c240f12e5b40 Solution Problem Understanding We are given a sequence of planar displacement vectors, each representing a move from the origin or from the current position. For every vector, we are allowed to choose its direction independently: we either add it as given...

CF 981B - Businessmen Problems Rating: 1000 Tags: sortings Model: gpt-5-3-mini Solve time: 1m 12s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a328490-05a4-83ec-983e-9f0d55973968 Solution Problem Understanding Two companies each own a collection of chemical elements, where every element is identified by a large integer key. Each occurrence of an element also carries a profit value that the company earns if it decides to present that element at the exhibition. The companies want...

CF 922D - Robot Vacuum Cleaner Rating: 1800 Tags: greedy, sortings Model: gpt-5-5 Solve time: 1m 20s Verified: yes (1/1 samples) Solution Problem Understanding We are given several short strings, each consisting only of the characters s and h . We are allowed to rearrange these strings in any order and then concatenate them into one long string. Once the final string is formed, we measure its “noise” as the...

CF 998B - Cutting Rating: 1200 Tags: dp, greedy, sortings Model: gpt-5-3-mini Solve time: 1m 4s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a329797-db90-83ec-b163-c4de935bce59 Solution Problem Understanding We are given a sequence of integers and we are allowed to split it into contiguous segments by making cuts between adjacent elements. Each segment must satisfy a structural constraint: the number of even values inside the segment must equal the number of odd values....

VK Cup 2018 - Round 3

VK Cup 2018 - Round 3 Special | 1 problems | 0/1 verified | Difficulty 1700-1700 | 2m 7s # Problem Rating Tags Accepted Time ✓ B Resource Distribution 1700 binary-search, implementation, sortings 2,350 2m 7s

CF 925B - Resource Distribution

CF 925B - Resource Distribution Rating: 1700 Tags: binary search, implementation, sortings Solve time: 2m 7s Verified: no Solution Problem Understanding We are given a pool of servers, each with a fixed capacity measured in resource units. Two independent services must be deployed, and each service can use several servers at the same time. When a service uses multiple servers, its total load is split evenly across them, so each...

Codeforces Round 467 (Div. 2)

Codeforces Round 467 (Div. 2) Div. 2 | 2 problems | 2/2 verified | Difficulty 800-1400 | 2m 7s # Problem Rating Tags Accepted Time ✓ A Olympiad 800 implementation, sortings 16,399 1m 2s ✓ B Vile Grasshoppers 1400 brute-force, math, number-theory 7,256 1m 5s ✓

CF 937A - Olympiad

CF 937A - Olympiad Rating: 800 Tags: implementation, sortings Solve time: 1m 2s Verified: yes Solution Problem Understanding We are given a list of participant scores, and we need to count how many different ways we can choose a group of participants to receive diplomas under a very specific rule. A valid group is determined by picking a score threshold. Once a participant with some score is included, every participant...

CF 940A - Points on the line

CF 940A - Points on the line Rating: 1200 Tags: brute force, greedy, sortings Solve time: 3m 1s Verified: yes Solution Problem Understanding We are given several points placed on a number line. Each point is just a single integer coordinate. We want to keep a subset of these points such that the spread of the remaining points is controlled, specifically the difference between the largest and smallest kept point...

Codeforces Round 466 (Div. 2)

Codeforces Round 466 (Div. 2) Div. 2 | 3 problems | 3/3 verified | Difficulty 1200-2000 | 5m 58s # Problem Rating Tags Accepted Time ✓ A Points on the line 1200 brute-force, greedy, sortings 8,815 3m 1s ✓ B Our Tanya is Crying Out Loud 1400 dp, greedy 9,505 1m 11s ✓ E Cashback 2000 data-structures, dp, greedy 4,390 1m 46s ✓

CF 949D - Curfew

CF 949D - Curfew Rating: 2300 Tags: binary search, brute force, greedy, sortings Solve time: 3m 41s Verified: no Solution Problem Understanding There are n rooms arranged in a line. Each room must end up with exactly b students being counted by inspectors, but initially the distribution is arbitrary as an array a[i] , and the total number of students equals n · b , so globally there is just...

Educational Codeforces Round 40 (Rated for Div. 2)

Educational Codeforces Round 40 (Rated for Div. 2) Div. 2 | 5 problems | 4/5 verified | Difficulty 800-2200 | 8m 36s # Problem Rating Tags Accepted Time ✓ A Diagonal Walking 800 implementation 11,046 1m ✓ B String Typing 1400 implementation, strings 7,789 1m 9s ✓ E Water Taps 2000 binary-search, greedy, sortings 2,095 1m 37s F Runner's Problem 2100 dp, matrices, sortings 1,377 3m 11s ✓ I Yet...

CF 954F - Runner's Problem

CF 954F - Runner's Problem Rating: 2100 Tags: dp, matrices, sortings Solve time: 3m 11s Verified: yes Solution Problem Understanding We are given a 3 by m grid where movement is always one column to the right and can also shift vertically by at most one row. The journey starts in the middle row of the first column and must end in the same middle row at the last column....

CF 954E - Water Taps

CF 954E - Water Taps Rating: 2000 Tags: binary search, greedy, sortings Solve time: 1m 37s Verified: no Solution Problem Understanding Each tap contributes a controllable flow of water, but every tap has a fixed temperature. You are allowed to choose a real-valued flow rate for each tap between zero and its maximum capacity. The final mixture has a temperature equal to a weighted average of all active taps, where...

Divide by Zero 2018 and Codeforces Round 474 (Div. 1 + Div. 2, combined)

Divide by Zero 2018 and Codeforces Round 474 (Div. 1 + Div. 2, combined) Div. 1+2 | 4 problems | 3/4 verified | Difficulty 1200-2900 | 6m 51s # Problem Rating Tags Accepted Time ✓ A Check the string 1200 implementation 8,786 1m 4s ✓ B Minimize the error 1500 data-structures, greedy, sortings 12,382 1m 14s ✓ E Alternating Tree 2300 combinatorics, dfs-and-similar, divide-and-conquer 2,269 2m 1s G Bandit Blues...

CF 960B - Minimize the error

CF 960B - Minimize the error Rating: 1500 Tags: data structures, greedy, sortings Solve time: 1m 14s Verified: yes Solution Problem Understanding We are working with two integer arrays of equal length. Each position contributes independently to a total “error”, where the error of an index is the square of the difference between the two values at that index. The total cost is the sum of these squared differences over...

CF 967B - Watering System

CF 967B - Watering System Rating: 1000 Tags: math, sortings Solve time: 1m 28s Verified: yes Solution Problem Understanding We are given a system of pipe holes, each hole having a fixed size that determines how much water it can drain when water is poured into the system. Arkady pours a fixed amount of water, but only one hole, the first one, is considered useful to him. His goal is...

Codeforces Round 477 (rated, Div. 2, based on VK Cup 2018 Round 3)

Codeforces Round 477 (rated, Div. 2, based on VK Cup 2018 Round 3) Div. 2 | 2 problems | 1/2 verified | Difficulty 1000-1100 | 1m 55s # Problem Rating Tags Accepted Time ✓ A Mind the Gap 1100 implementation 4,641 27s B Watering System 1000 math, sortings 7,885 1m 28s ✓

CF 976E - Well played!

CF 976E - Well played! Rating: 2100 Tags: greedy, sortings Solve time: 1m 55s Verified: yes Solution Problem Understanding Each creature starts with a fixed health value and a fixed damage value. We are allowed to improve the army using two global operations. One operation increases a creature’s health by doubling it, and the other operation overwrites a creature’s damage with its current health. The second operation is valuable only...

Educational Codeforces Round 43 (Rated for Div. 2)

Educational Codeforces Round 43 (Rated for Div. 2) Div. 2 | 3 problems | 2/3 verified | Difficulty 800-2100 | 4m 57s # Problem Rating Tags Accepted Time ✓ A Minimum Binary Number 800 implementation 10,974 1m 46s C Nested Segments 1500 greedy, implementation, sortings 10,625 1m 16s ✓ E Well played! 2100 greedy, sortings 2,552 1m 55s ✓

CF 976C - Nested Segments

CF 976C - Nested Segments Rating: 1500 Tags: greedy, implementation, sortings Solve time: 1m 16s Verified: yes Solution Problem Understanding We are given a collection of closed intervals on a number line. Each interval represents a segment with a left endpoint and a right endpoint, and we need to determine whether there exists a pair of distinct segments such that one is fully contained inside the other. Formally, for two...

Codeforces Round 479 (Div. 3)

Codeforces Round 479 (Div. 3) Div. 3 | 5 problems | 3/5 verified | Difficulty 800-1700 | 6m 59s # Problem Rating Tags Accepted Time ✓ A Wrong Subtraction 800 implementation 217,381 1m 11s ✓ B Two-gram 900 implementation, strings 49,745 1m 15s C Less or Equal 1200 sortings 43,322 1m 33s ✓ D Divide by three, multiply by two 1400 dfs-and-similar, math, sortings 20,523 1m 26s ✓ F Consecutive...

CF 977D - Divide by three, multiply by two

CF 977D - Divide by three, multiply by two Rating: 1400 Tags: dfs and similar, math, sortings Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given a multiset of integers that originally came from a single starting value that Polycarp repeatedly transformed. Each transformation either doubles the current number or divides it by three when it is divisible. After applying these operations exactly $n-1$ times, we observe...

CF 977C - Less or Equal

CF 977C - Less or Equal Rating: 1200 Tags: sortings Solve time: 1m 33s Verified: yes Solution Problem Understanding We are given a list of integers and asked to construct a value $x$ between 1 and $10^9$ such that exactly $k$ elements of the list are less than or equal to $x$. If no such value exists, we must output $-1$. A useful way to think about this is that...

CF 978G - Petya's Exams

CF 978G - Petya's Exams Rating: 1700 Tags: greedy, implementation, sortings Solve time: 1m 27s Verified: no Solution Problem Understanding We are given a timeline of $n$ days and a set of $m$ exams, each fixed to happen on exactly one specific day. Every exam also comes with a preparation window that starts after its announcement day and ends the day before the exam itself, plus a required number of...

CF 984A - Game

CF 984A - Game Rating: 800 Tags: sortings Solve time: 1m 30s Verified: yes Solution Problem Understanding We are given a list of integers placed on a board. Two players alternate turns removing exactly one number from the board. After exactly $n-1$ removals, only a single number remains, and that number is the outcome of the game. The players have opposing goals. The first player removes numbers in a way...

Codeforces Round 483 (Div. 2) [Thanks, Botan Investments and Victor Shaburov!]

Codeforces Round 483 (Div. 2) [Thanks, Botan Investments and Victor Shaburov!] Div. 2 | 1 problems | 1/1 verified | Difficulty 800-800 | 1m 30s # Problem Rating Tags Accepted Time ✓ A Game 800 sortings 20,742 1m 30s ✓

Codeforces Round 486 (Div. 3)

Codeforces Round 486 (Div. 3) Div. 3 | 3 problems | 1/3 verified | Difficulty 1100-2100 | 4m 21s # Problem Rating Tags Accepted Time ✓ B Substrings Sort 1100 sortings, strings 20,279 1m 22s ✓ C Equal Sums 1400 implementation, sortings 11,135 1m 23s F Rain and Umbrellas 2100 dp 2,776 1m 36s

CF 988C - Equal Sums

CF 988C - Equal Sums Rating: 1400 Tags: implementation, sortings Solve time: 1m 23s Verified: no Solution Problem Understanding We are given several independent integer arrays. From each array we are allowed to remove exactly one element, and this creates a “modified sum” for that array, meaning the original sum minus the removed element. The task is to pick two different arrays and choose one removal position in each so...

CF 988B - Substrings Sort

CF 988B - Substrings Sort Rating: 1100 Tags: sortings, strings Solve time: 1m 22s Verified: yes Solution Problem Understanding We are given a collection of strings, and we are allowed to rearrange them in any order. After rearranging, we want a very specific nesting property: every string must contain all strings that appear before it as substrings. In other words, if we line up the strings from first to last,...

CF 989D - A Shade of Moonlight

CF 989D - A Shade of Moonlight Rating: 2500 Tags: binary search, geometry, math, sortings, two pointers Solve time: 2m 41s Verified: no Solution Problem Understanding We are given several “clouds” moving along a line. Each cloud is a segment of fixed length $l$, initially placed at position $x_i$, and then moving over time with constant velocity $v_i + w$, where $v_i$ is either $+1$ or $-1$, and $w$ is...

CF 992A - Nastya and an Array

CF 992A - Nastya and an Array Rating: 800 Tags: implementation, sortings Solve time: 1m 8s Verified: yes Solution Problem Understanding We are given a list of integers, and we are allowed to repeatedly apply an operation that changes the array in a very specific way: in one move, we choose an integer value and add it to every element that is currently non-zero. Zeros stay untouched during that operation....

Codeforces Round 489 (Div. 2)

Codeforces Round 489 (Div. 2) Div. 2 | 2 problems | 2/2 verified | Difficulty 800-1600 | 2m 25s # Problem Rating Tags Accepted Time ✓ A Nastya and an Array 800 implementation, sortings 14,315 1m 8s ✓ B Nastya Studies Informatics 1600 math, number-theory 6,766 1m 17s ✓

Codeforces Round 488 by NEAR (Div. 2)

Codeforces Round 488 by NEAR (Div. 2) Div. 2 | 2 problems | 2/2 verified | Difficulty 800-1400 | 8m 33s # Problem Rating Tags Accepted Time ✓ A Fingerprints 800 implementation 15,211 4m 11s ✓ B Knights of a Polygonal Table 1400 greedy, implementation, sortings 6,045 4m 22s ✓

CF 994B - Knights of a Polygonal Table

CF 994B - Knights of a Polygonal Table Rating: 1400 Tags: greedy, implementation, sortings Solve time: 4m 22s Verified: yes Solution Problem Understanding Each knight comes with two attributes, a fighting strength and a stash of coins. A knight is only able to defeat knights with strictly smaller strength, and every victory transfers the defeated knight’s coins to the winner. However, there is a global constraint: no knight is willing...

Educational Codeforces Round 46 (Rated for Div. 2)

Educational Codeforces Round 46 (Rated for Div. 2) Div. 2 | 4 problems | 2/4 verified | Difficulty 1500-2700 | 7m 8s # Problem Rating Tags Accepted Time ✓ B Light It Up 1500 greedy 6,162 1m 52s ✓ C Covered Points Count 1700 data-structures, implementation, sortings 8,431 1m 14s ✓ F One Occurrence 2400 data-structures, divide-and-conquer 4,835 1m 52s G Two-Paths 2700 data-structures, dp, trees 715 2m 10s

CF 1000C - Covered Points Count

CF 1000C - Covered Points Count Rating: 1700 Tags: data structures, implementation, sortings Solve time: 1m 14s Verified: yes Solution Problem Understanding We are given a collection of segments on a very large number line. Each segment covers every integer point between its endpoints, including both ends. Different segments may overlap in arbitrary ways: they can be disjoint, nested, identical, or partially intersecting. The task is not to find the...

CF 1005E2 - Median on Segments (General Case Edition)

CF 1005E2 - Median on Segments (General Case Edition) Rating: 2400 Tags: sortings Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given a sequence of integers and a fixed value $m$. The task is to count how many contiguous subarrays have the property that when you sort the subarray, its median equals exactly $m$, where for even-length subarrays the median is defined as the left middle element....

CF 1005E1 - Median on Segments (Permutations Edition)

CF 1005E1 - Median on Segments (Permutations Edition) Rating: 1800 Tags: sortings Solve time: 1m 41s Verified: no Solution Problem Understanding We are given a permutation of the integers from 1 to n, and a distinguished value m that appears exactly once somewhere in the array. The task is to count how many contiguous subarrays have the property that, if we sort that subarray, the median element equals m. The...

Codeforces Round 498 (Div. 3)

Codeforces Round 498 (Div. 3) Div. 3 | 6 problems | 4/6 verified | Difficulty 800-2100 | 9m 42s # Problem Rating Tags Accepted Time ✓ A Adjacent Replacements 800 implementation 22,872 1m 42s ✓ B Polycarp's Practice 1200 greedy, implementation, sortings 14,655 1m 47s C Three Parts of the Array 1200 binary-search, data-structures, two-pointers 25,307 1m 13s ✓ D Two Strings Swaps 1700 implementation 6,477 1m 39s E Military...

CF 1006B - Polycarp's Practice

CF 1006B - Polycarp's Practice Rating: 1200 Tags: greedy, implementation, sortings Solve time: 1m 47s Verified: no Solution Problem Understanding We are given a sequence of problem difficulties in a fixed order, and we must split this sequence into exactly k consecutive segments. Each segment corresponds to one day of practice, and every problem must belong to exactly one segment. The restriction is that we cannot reorder, skip, or split...

Codeforces Round 497 (Div. 1)

Codeforces Round 497 (Div. 1) Div. 1 | 5 problems | 3/5 verified | Difficulty 1300-3400 | 11m 58s # Problem Rating Tags Accepted Time ✓ A Reorder the Array 1300 combinatorics, data-structures, math 13,066 3m 11s ✓ B Pave the Parallelepiped 2400 bitmasks, brute-force, combinatorics 1,037 2m 4s ✓ C Guess two numbers 3000 binary-search, interactive 527 2m 36s D Ants 3200 2-sat, data-structures, trees 322 2m 5s ✓...

CF 1007A - Reorder the Array

CF 1007A - Reorder the Array Rating: 1300 Tags: combinatorics, data structures, math, sortings, two pointers Solve time: 3m 11s Verified: yes Solution Problem Understanding We are given an array of numbers and allowed to freely reorder them. After rearranging, we compare the new array against the original array position by position. A position is considered “good” if the value placed there after permutation is strictly larger than the value...

Codeforces Round 497 (Div. 2)

Codeforces Round 497 (Div. 2) Div. 2 | 2 problems | 2/2 verified | Difficulty 900-1000 | 2m 30s # Problem Rating Tags Accepted Time ✓ A Romaji 900 implementation, strings 16,359 1m 17s ✓ B Turn the Rectangles 1000 greedy, sortings 12,562 1m 13s ✓

CF 1008B - Turn the Rectangles

CF 1008B - Turn the Rectangles Rating: 1000 Tags: greedy, sortings Solve time: 1m 13s Verified: yes Solution Problem Understanding We are given a sequence of rectangular tiles placed in a fixed left-to-right order. Each tile has two possible orientations: we can either keep it as width-by-height or rotate it by 90 degrees, which swaps the two values. After choosing an orientation independently for every tile, we look only at...

Codeforces Round 499 (Div. 2)

Codeforces Round 499 (Div. 2) Div. 2 | 2 problems | 2/2 verified | Difficulty 900-1200 | 3m 8s # Problem Rating Tags Accepted Time ✓ A Stages 900 greedy, implementation, sortings 13,262 1m 43s ✓ B Planning The Expedition 1200 binary-search, brute-force, implementation 11,026 1m 25s ✓

CF 1011A - Stages

CF 1011A - Stages Rating: 900 Tags: greedy, implementation, sortings Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given a multiset of characters, each character representing a rocket stage with an intrinsic cost equal to its position in the alphabet. From this multiset we must pick exactly k distinct stages and arrange them in an order that respects a strict compatibility rule: when a stage with letter...

Codeforces Round 500 (Div. 1) [based on EJOI]

Codeforces Round 500 (Div. 1) [based on EJOI] Div. 1 | 6 problems | 3/6 verified | Difficulty 1500-3400 | 15m 11s # Problem Rating Tags Accepted Time ✓ A Photo of The Sky 1500 brute-force, implementation, math 6,689 1m 29s ✓ B Chemical table 1900 constructive-algorithms, dfs-and-similar, dsu 4,385 1m 39s ✓ C Hills 1900 dp 3,827 2m 10s D AB-Strings 2800 constructive-algorithms, strings 426 2m 15s E Cycle...

CF 1012A - Photo of The Sky

CF 1012A - Photo of The Sky Rating: 1500 Tags: brute force, implementation, math, sortings Solve time: 1m 29s Verified: yes Solution Problem Understanding We are given a multiset of numbers of size 2n , and we are told that these numbers originally came from n points in the plane, where each point contributes exactly two integers: its x-coordinate and its y-coordinate. The catch is that the pairing is completely...

Codeforces Round 501 (Div. 3)

Codeforces Round 501 (Div. 3) Div. 3 | 7 problems | 5/7 verified | Difficulty 800-2300 | 18m # Problem Rating Tags Accepted Time ✓ A Points in Segments 800 implementation 22,434 1m 28s ✓ B Obtaining the String 1200 implementation 12,411 1m 35s ✓ C Songs Compression 1100 sortings 21,394 3m 28s ✓ D Walking Between Houses 1600 constructive-algorithms, greedy 8,960 4m 18s ✓ E1 Stars Drawing (Easy Edition)...

CF 1015C - Songs Compression

CF 1015C - Songs Compression Rating: 1100 Tags: sortings Solve time: 3m 28s Verified: yes Solution Problem Understanding We are given a collection of songs, each with an original size and a smaller size if we choose to compress it. All songs must be copied onto a flash drive whose total capacity is fixed. The only decision available is which songs to compress. Compressing a song replaces its size with...

CF 1019D - Large Triangle

CF 1019D - Large Triangle Rating: 2700 Tags: binary search, geometry, sortings Solve time: 2m 44s Verified: yes Solution Problem Understanding We are given a set of points on a plane, each point representing a city. The task is to select three distinct cities such that the triangle formed by them has a prescribed area $S$. If no such triple exists, we must report failure. The output is not the...

Codeforces Round 505 (rated, Div. 1 + Div. 2, based on VK Cup 2018 Final)

Codeforces Round 505 (rated, Div. 1 + Div. 2, based on VK Cup 2018 Final) Div. 1+2 | 7 problems | 5/7 verified | Difficulty 900-3200 | 26m 51s # Problem Rating Tags Accepted Time ✓ A Doggo Recoloring 900 implementation, sortings 16,523 2m 13s ✓ B Weakened Common Divisor 1600 brute-force, greedy, number-theory 8,508 2m 43s ✓ C Plasticine zebra 1600 constructive-algorithms, implementation 6,491 5m 11s D Recovering BST...

CF 1025A - Doggo Recoloring

CF 1025A - Doggo Recoloring Rating: 900 Tags: implementation, sortings Solve time: 2m 13s Verified: yes Solution Problem Understanding We are given a string representing the colors of a line of puppies, where each character is a color from 'a' to 'z'. The goal is to determine whether we can transform this string so that all characters become the same, using a very specific operation. The operation allows us to...

AIM Tech Round 5 (rated, Div. 1 + Div. 2)

AIM Tech Round 5 (rated, Div. 1 + Div. 2) Div. 1+2 | 8 problems | 3/8 verified | Difficulty 800-3000 | 21m 57s # Problem Rating Tags Accepted Time ✓ A Find Square 800 implementation 11,517 1m 44s ✓ B Unnatural Conditions 1200 constructive-algorithms, math 10,234 2m 29s C Rectangles 1600 geometry, implementation, sortings 5,050 2m 30s ✓ D Order book 2100 combinatorics, data-structures, greedy 1,822 2m 46s E...

CF 1028C - Rectangles

CF 1028C - Rectangles Rating: 1600 Tags: geometry, implementation, sortings Solve time: 2m 30s Verified: yes Solution Problem Understanding We are given a collection of axis-aligned rectangles on a 2D integer grid. Each rectangle is described by its bottom-left corner and top-right corner, and it includes its boundary as well as its interior. The key guarantee is that if we remove any one rectangle, the remaining rectangles still share at...

Codeforces Round 506 (Div. 3)

Codeforces Round 506 (Div. 3) Div. 3 | 6 problems | 5/6 verified | Difficulty 1200-2100 | 22m 31s # Problem Rating Tags Accepted Time ✓ A Many Equal Substrings 1300 implementation, strings 13,430 2m 24s ✓ B Creating the Contest 1200 dp, greedy, math 18,462 2m 25s ✓ C Maximal Intersection 1600 greedy, math, sortings 8,272 2m 50s ✓ D Concatenated Multiples 1900 implementation, math 4,234 5m 17s E...

CF 1029C - Maximal Intersection

CF 1029C - Maximal Intersection Rating: 1600 Tags: greedy, math, sortings Solve time: 2m 50s Verified: yes Solution Problem Understanding We are given a collection of segments on a number line, and we want to understand how much they overlap if we remove exactly one of them. For any subset of segments, their common intersection is also a segment (or empty), and its length is determined by how tightly all...

Codeforces Round 737 (Div. 2)

Codeforces Round 737 (Div. 2) Div. 2 | 5 problems | 3/5 verified | Difficulty 800-2800 | 19m 9s # Problem Rating Tags Accepted Time ✓ A Ezzat and Two Subsequences 800 brute-force, math, sortings 29,144 3m 16s ✓ B Moamen and k-subarrays 1100 greedy, sortings 24,608 3m 16s ✓ C Moamen and XOR 1700 bitmasks, combinatorics, dp 10,496 5m 29s ✓ D Ezzat and Grid 2200 data-structures, dp, greedy...

Codeforces Global Round 9

Codeforces Global Round 9 Global | 9 problems | 1/9 verified | Difficulty 1100-3500 | 36m 35s # Problem Rating Tags Accepted Time ✓ A Sign Flipping 1100 constructive-algorithms, math 18,842 2m 18s B Neighbor Grid 1200 constructive-algorithms, greedy 17,850 2m 18s C Element Extermination 1400 constructive-algorithms, data-structures, greedy 22,944 2m 34s D Replace by MEX 1900 brute-force, constructive-algorithms, sortings 10,140 1m 24s E Inversion SwapSort 2500 constructive-algorithms, greedy, sortings...

CF 1039C - Network Safety

CF 1039C - Network Safety Rating: 2200 Tags: dfs and similar, dsu, graphs, math, sortings Solve time: 8m 24s Verified: yes Solution Problem Understanding We are given a network of servers where each server has an integer label (an encryption key) in a fixed bit range. Some pairs of servers are connected, and a connection is considered safe only if the two endpoints currently hold different values. A virus is...

Codeforces Round 509 (Div. 2)

Codeforces Round 509 (Div. 2) Div. 2 | 3 problems | 1/3 verified | Difficulty 800-1900 | 13m 23s # Problem Rating Tags Accepted Time ✓ A Heist 800 greedy, implementation, sortings 26,842 2m 41s ✓ C Coffee Break 1600 binary-search, data-structures, greedy 10,236 4m 36s E Tree Reconstruction 1900 constructive-algorithms, data-structures, graphs 3,854 6m 6s

CF 1041A - Heist

CF 1041A - Heist Rating: 800 Tags: greedy, implementation, sortings Solve time: 2m 41s Verified: yes Solution Problem Understanding We are given a set of keyboard indices that survived a burglary. The key hidden structure is that before the theft, all keyboards formed one continuous block of integers, something like x, x+1, x+2, and so on up to some unknown length. After the theft, some of those consecutive integers are...

CF 1043E - Train Hard, Win Easy

CF 1043E - Train Hard, Win Easy Rating: 1900 Tags: constructive algorithms, greedy, math, sortings Solve time: 4m 14s Verified: yes Solution Problem Understanding We are given a set of participants, each described by two numbers. These two numbers represent how much penalty a participant contributes depending on whether they solve the first task or the second task in a two-person training contest. When two participants form a team, they...

CF 1725F - Field Photography

CF 1725F - Field Photography Rating: 2100 Tags: bitmasks, data structures, sortings Solve time: 2m 55s Verified: no Solution Problem Understanding Each row initially contains a contiguous block of contestants placed on an extremely large integer line of columns. Row $i$ occupies every position from $L_i$ to $R_i$, so geometrically each row is just a closed interval. We are allowed to shift an entire row left or right by any...

CF 1558F - Strange Sort

CF 1558F - Strange Sort Rating: 3300 Tags: data structures, sortings Solve time: 5m 6s Verified: no Solution Problem Understanding We are given a permutation that is repeatedly processed by a very specific “two-phase bubble-like” routine. In each iteration, we do not scan all adjacent pairs; instead we alternate between touching only odd edges and only even edges. On odd-numbered iterations we compare and possibly swap positions (1,2), (3,4), (5,6),...

CF 1557B - Moamen and k-subarrays

CF 1557B - Moamen and k-subarrays Rating: 1100 Tags: greedy, sortings Solve time: 3m 16s Verified: yes Solution Problem Understanding We are given an array of distinct integers and allowed to perform a very specific transformation exactly once. First, we cut the array into exactly k contiguous pieces, each piece non-empty. Then we are allowed to permute these pieces arbitrarily, and finally we glue them back together in that new...

CF 1557A - Ezzat and Two Subsequences

CF 1557A - Ezzat and Two Subsequences Rating: 800 Tags: brute force, math, sortings Solve time: 3m 16s Verified: yes Solution Problem Understanding We are given an array of integers, and we must split it into two non-empty groups while preserving every element exactly once. Each group has a score equal to its arithmetic mean, and the goal is to maximize the sum of these two means. So if we...

CF 1552C - Maximize the Intersections

CF 1552C - Maximize the Intersections Rating: 1800 Tags: combinatorics, constructive algorithms, geometry, greedy, sortings Solve time: 7m 19s Verified: no Solution Problem Understanding We are given points placed around a circle in clockwise order. Some of these points are already connected by chords, and these initial chords never share endpoints. The remaining points are also distinct endpoints that must be paired up into new chords so that in the...

CF 1552E - Colors and Intervals

CF 1552E - Colors and Intervals Rating: 2300 Tags: constructive algorithms, data structures, greedy, sortings Solve time: 7m 14s Verified: no Solution Problem Understanding We are given a long line of positions from 1 to n·k, each position painted with one of n colors, and each color appears exactly k times. For every color i we must choose exactly one interval [a_i, b_i] such that both endpoints belong to positions...

CF 1386B - Mixture

CF 1386B - Mixture Rating: 2900 Tags: *special, data structures, geometry, math, sortings Solve time: 7m 15s Verified: no Solution Problem Understanding We are maintaining a dynamic multiset of 3D vectors, each vector representing the amounts of salt, pepper, and garlic powder in a bottle. After each update, either adding or removing a bottle, we must determine the smallest number of available bottles whose positive linear combination can produce a...

CF 1383D - Rearrange

CF 1383D - Rearrange Rating: 2800 Tags: brute force, constructive algorithms, graphs, greedy, sortings Solve time: 5m 10s Verified: no Solution Problem Understanding We are given a complete permutation of numbers from 1 to $n \cdot m$ arranged in an $n \times m$ grid. From this grid we extract two small summaries: the set of row maxima and the set of column maxima. The task is to construct a new...

Educational Codeforces Round 91 (Rated for Div. 2)

Educational Codeforces Round 91 (Rated for Div. 2) Div. 2 | 5 problems | 3/5 verified | Difficulty 1400-2600 | 22m 23s # Problem Rating Tags Accepted Time ✓ B Universal Solution 1400 greedy 15,281 5m 4s C Create The Teams 1400 brute-force, dp, greedy 22,708 1m 31s ✓ E Merging Towers 2300 data-structures, dsu, implementation 2,409 7m 10s ✓ F Strange Addition 2600 data-structures, dp, matrices 891 2m 24s...

CF 1379C - Choosing flowers

CF 1379C - Choosing flowers Rating: 2000 Tags: binary search, brute force, data structures, dfs and similar, dp, greedy, sortings, two pointers Solve time: 6m 47s Verified: no Solution Problem Understanding We are choosing exactly $n$ flowers from $m$ available types, where each type can be used an unlimited number of times. The value of picking flowers is not linear per flower, instead each type behaves like a diminishing reward...

CF 1375E - Inversion SwapSort

CF 1375E - Inversion SwapSort Rating: 2500 Tags: constructive algorithms, greedy, sortings Solve time: 5m 30s Verified: yes Solution Problem Understanding We are given a sequence of numbers, and we are allowed to swap any two positions, but only if those two positions currently form an inversion in the original array. An inversion is simply a pair of indices where the left value is strictly larger than the right value....

CF 1374F - Cyclic Shifts Sorting

CF 1374F - Cyclic Shifts Sorting Rating: 2400 Tags: brute force, constructive algorithms, implementation, sortings Solve time: 5m 28s Verified: no Solution Problem Understanding We are given an array and a very specific primitive operation: we can pick any position and rotate a block of three consecutive elements to the right. That means a local triple [x, y, z] becomes [z, x, y] . Repeating this operation many times, we...

CF 1374E1 - Reading Books (easy version)

CF 1374E1 - Reading Books (easy version) Rating: 1600 Tags: data structures, greedy, sortings Solve time: 2m 55s Verified: yes Solution Problem Understanding We are given a collection of books, each with a reading time and two independent preference flags, one for Alice and one for Bob. We must select a subset of books such that Alice has at least $k$ liked books in the chosen subset and Bob also...

CF 1367F2 - Flying Sort (Hard Version)

CF 1367F2 - Flying Sort (Hard Version) Rating: 2400 Tags: binary search, data structures, dp, greedy, sortings, two pointers Solve time: 4m 7s Verified: no Solution Problem Understanding We are given a sequence of numbers and a very specific way to reorder it. In one operation, we pick any element and either push it all the way to the front or all the way to the back of the array....

CF 1367D - Task On The Board

CF 1367D - Task On The Board Rating: 1800 Tags: constructive algorithms, greedy, implementation, sortings Solve time: 6m 59s Verified: no Solution Problem Understanding We are given a multiset of lowercase letters, initially written as a string $s$. From this multiset, some letters are discarded and the remaining letters are rearranged arbitrarily to form a new string $t$. The length of $t$ is fixed and given as $m$, and alongside...

CF 1365F - Swaps Again

CF 1365F - Swaps Again Rating: 2100 Tags: constructive algorithms, implementation, sortings Solve time: 2m 28s Verified: no Solution Problem Understanding We are given two arrays of equal length and a very specific transformation rule. Starting from the first array, we are allowed to repeatedly pick a split size and swap two equal-length blocks: the prefix of that size and the suffix of the same size. Everything in the middle,...

CF 1360C - Similar Pairs

CF 1360C - Similar Pairs Rating: 1100 Tags: constructive algorithms, graph matchings, greedy, sortings Solve time: 4m 42s Verified: yes Solution Problem Understanding We are given several independent arrays, each with an even number of elements. For each array, we must decide whether it is possible to split all elements into disjoint pairs such that every number belongs to exactly one pair and each pair satisfies a compatibility rule. Two...

Codeforces Round 638 (Div. 2)

Codeforces Round 638 (Div. 2) Div. 2 | 4 problems | 1/4 verified | Difficulty 1400-2400 | 19m 23s # Problem Rating Tags Accepted Time ✓ B Phoenix and Beauty 1400 constructive-algorithms, data-structures, greedy 27,483 5m 10s C Phoenix and Distribution 1600 constructive-algorithms, greedy, sortings 15,480 5m 1s D Phoenix and Science 1900 binary-search, constructive-algorithms, greedy 9,341 2m 53s E Phoenix and Berries 2400 brute-force, dp, greedy 2,429 6m 19s...

CF 1348B - Phoenix and Beauty

CF 1348B - Phoenix and Beauty Rating: 1400 Tags: constructive algorithms, data structures, greedy, sortings Solve time: 5m 10s Verified: no Solution Problem Understanding We are given an array and allowed to insert additional values anywhere inside it, where every inserted value must stay within the same value range as the original array elements. After these insertions, we want the resulting array to satisfy a very rigid condition: every contiguous...

CF 1348C - Phoenix and Distribution

CF 1348C - Phoenix and Distribution Rating: 1600 Tags: constructive algorithms, greedy, sortings, strings Solve time: 5m 1s Verified: no Solution Problem Understanding We are given a string made of lowercase letters and we are allowed to split all of its characters into exactly k non-empty groups. Inside each group, we can reorder characters arbitrarily, so each group is effectively just a multiset of letters that we later sort into...

CF 1346C - Spring Cleaning

CF 1346C - Spring Cleaning Rating: 1600 Tags: *special, greedy, sortings Solve time: 5m 16s Verified: no Solution Problem Understanding We are given a row of shelves, each holding some number of books. The goal is to reach a state where every shelf has at most k books. We are allowed to modify the configuration using two operations. The first operation is local: we can pick one shelf and remove...

CF 1343E - Weights Distributing

CF 1343E - Weights Distributing Rating: 2100 Tags: brute force, graphs, greedy, shortest paths, sortings Solve time: 2m 40s Verified: yes Solution Problem Understanding We are given a connected undirected graph where each edge represents a road, but the roads do not yet have fixed costs. Instead, we are also given a list of prices, and we must assign exactly one price to each edge. After the assignment, Mike travels...

CF 1339B - Sorted Adjacent Differences

CF 1339B - Sorted Adjacent Differences Rating: 1200 Tags: constructive algorithms, sortings Solve time: 3m 50s Verified: no Solution Problem Understanding We are given several independent arrays, and for each one we must reorder its elements into a sequence where the absolute differences between neighboring elements never decrease as we move from left to right. In other words, once we start placing numbers in a line, the gaps between consecutive...

CF 1335C - Two Teams Composing

CF 1335C - Two Teams Composing Rating: 1100 Tags: binary search, greedy, implementation, sortings Solve time: 2m 50s Verified: no Solution Problem Understanding We are given a multiset of student skills for each test case. From this pool we must form two disjoint groups of students, both of the same size, say $x$. The first group is constrained to have all distinct values, so every chosen student must contribute a...

Codeforces Round 627 (Div. 3)

Codeforces Round 627 (Div. 3) Div. 3 | 3 problems | 1/3 verified | Difficulty 900-1400 | 5m 54s # Problem Rating Tags Accepted Time ✓ A Yet Another Tetris Problem 900 implementation, number-theory 27,310 3m 14s C Frog Jumps 30,509 D Pair of Topics 1400 binary-search, data-structures, sortings 34,073 2m 40s ✓

CF 1324D - Pair of Topics

CF 1324D - Pair of Topics Rating: 1400 Tags: binary search, data structures, sortings, two pointers Solve time: 2m 40s Verified: yes Solution Problem Understanding We are given a list of topics, each topic carrying two different scores. One score measures how interesting the topic is for the teacher, and the other measures how interesting it is for students. For any two distinct topics $i$ and $j$, we want to...

Codeforces Round 625 (Div. 1, based on Technocup 2020 Final Round)

Codeforces Round 625 (Div. 1, based on Technocup 2020 Final Round) Div. 1 | 3 problems | 1/3 verified | Difficulty 1700-2500 | 10m 5s # Problem Rating Tags Accepted Time ✓ B Navigation System 1700 dfs-and-similar, graphs, shortest-paths 6,437 2m 48s ✓ C World of Darkraft: Battle for Azathoth 2000 brute-force, data-structures, sortings 3,426 2m 48s D Reachable Strings 2500 data-structures, hashing, strings 1,692 4m 29s

CF 1312B - Bogosort

CF 1312B - Bogosort Rating: 1000 Tags: constructive algorithms, sortings Solve time: 4m 47s Verified: no Solution Problem Understanding We are given an array of integers and are allowed to permute it arbitrarily. After rearranging, we assign each value to a position starting from 1. The array is considered valid if no two positions share the same value of the expression i - a[i] . In other words, if we...

Educational Codeforces Round 83 (Rated for Div. 2)

Educational Codeforces Round 83 (Rated for Div. 2) Div. 2 | 4 problems | 0/4 verified | Difficulty 1000-2600 | 9m 40s # Problem Rating Tags Accepted Time ✓ B Bogosort 1000 constructive-algorithms, sortings 39,027 4m 47s C Adding Powers 1400 bitmasks, greedy, implementation 18,342 1m 8s D Count the Arrays 1700 combinatorics, math 10,525 2m 54s G Autocompletion 2600 data-structures, dfs-and-similar, dp 1,081 51s

CF 1307D - Cow and Fields

CF 1307D - Cow and Fields Rating: 1900 Tags: binary search, data structures, dfs and similar, graphs, greedy, shortest paths, sortings Solve time: 1m 16s Verified: yes Solution Problem Understanding We are given an undirected, connected graph representing fields connected by roads. A traveler starts at node 1 and wants to reach node n using the shortest possible route. On top of the existing network, we are allowed to add...

CF 1297F - Movie Fan

CF 1297F - Movie Fan Rating: - Tags: *special, data structures, greedy, implementation, sortings Solve time: 2m 18s Verified: no Solution Problem Understanding We are given several movies, each movie has a time window during which it can be watched in the cinema. If a movie is watched inside its window, it is considered “on time”. If it is watched after its window ends, it becomes an online watch and...

CF 1297D - Bonus Distribution

CF 1297D - Bonus Distribution Rating: - Tags: *special, binary search, greedy, sortings Solve time: 3m 37s Verified: no Solution Problem Understanding Each employee has a fixed base salary, and we are allowed to distribute an additional integer bonus so that the total bonus across all employees is exactly k . After adding bonuses, each employee’s final salary becomes their original salary plus their assigned bonus. There are three structural...

CF 1296F - Berland Beauty

CF 1296F - Berland Beauty Rating: 2100 Tags: constructive algorithms, dfs and similar, greedy, sortings, trees Solve time: 7m 17s Verified: no Solution Problem Understanding We are given a connected network of $n$ stations connected by $n-1$ railway segments, which means the structure is a tree. Each edge in this tree has an unknown integer weight in the range from 1 to $10^6$. We are also given several observations from...

CF 1296D - Fight with Monsters

CF 1296D - Fight with Monsters Rating: 1500 Tags: greedy, sortings Solve time: 2m 49s Verified: no Solution Problem Understanding We are given a sequence of monsters standing in a fixed order. Each monster has a certain amount of health, and they must be defeated one after another from left to right. A fight with a monster is turn-based: first you strike, then the opponent strikes, repeating until the monster’s...

CF 1285E - Delete a Segment

CF 1285E - Delete a Segment Rating: 2300 Tags: brute force, constructive algorithms, data structures, dp, graphs, sortings, trees, two pointers Solve time: 3m 14s Verified: no Solution Problem Understanding We are given several intervals on a number line. Each interval represents a continuous segment of covered points. If multiple intervals overlap or touch, their combined covered region merges into a single continuous piece when we take the union. The...

CF 1284E - New Year and Castle Construction

CF 1284E - New Year and Castle Construction Rating: 2500 Tags: combinatorics, geometry, math, sortings Solve time: 7m 49s Verified: no Solution Problem Understanding We are given a set of points in the plane, with the restriction that no three points lie on a single line. For every point (p), we want to count how many subsets of exactly four other points can form a simple quadrilateral that strictly contains...

CF 1284D - New Year and Conference

CF 1284D - New Year and Conference Rating: 2100 Tags: binary search, data structures, hashing, sortings Solve time: 2m 35s Verified: yes Solution Problem Understanding Each lecture in the conference has two possible time schedules, depending on which venue is chosen. If we pick venue A, every lecture follows its A-interval. If we pick venue B, every lecture follows its B-interval. The key restriction is that a participant can attend...

CF 1284B - New Year and Ascent Sequence

CF 1284B - New Year and Ascent Sequence Rating: 1400 Tags: binary search, combinatorics, data structures, dp, implementation, sortings Solve time: 2m 36s Verified: yes Solution Problem Understanding We are given a collection of integer sequences, and we consider ordered pairs of them. For any pair of sequences $s_x$ and $s_y$, we concatenate them to form a longer sequence $s_x + s_y$. The goal is to count how many ordered...

CF 1282B1 - K for the Price of One (Easy Version)

CF 1282B1 - K for the Price of One (Easy Version) Rating: 1400 Tags: dp, greedy, sortings Solve time: 9m 50s Verified: no Solution Problem Understanding We are given several independent test cases. In each one, Vasya has a budget and a list of item prices. He wants to maximize how many items he can take from the store. The store has a special promotion with groups of two items....

CF 1282B2 - K for the Price of One (Hard Version)

CF 1282B2 - K for the Price of One (Hard Version) Rating: 1600 Tags: dp, greedy, sortings Solve time: 5m 59s Verified: no Solution Problem Understanding We are given a list of item prices and a budget. Vasya wants to maximize the number of items he acquires. He has two ways to buy: he can purchase a single item at its full price, or he can activate a bundle purchase...

CF 1270D - Strange Device

CF 1270D - Strange Device Rating: 1900 Tags: constructive algorithms, interactive, math, sortings Solve time: 2m 34s Verified: yes Solution Problem Understanding We are given an unknown array of distinct integers. We cannot read it directly. Instead, we can query any subset of exactly k positions, and the device returns the position and value of the element that would rank as the m -th smallest among those k values. The...

CF 1260D - A Game with Traps

CF 1260D - A Game with Traps Rating: 1900 Tags: binary search, dp, greedy, sortings Solve time: 10m 47s Verified: yes Solution Problem Understanding We are given a line of positions from 0 to n+1. A group of soldiers starts at position 0 together with the player character. Each soldier has a strength value, and traps placed along the line may kill soldiers whose strength is too low when they...

CF 1253D - Harmonious Graph

CF 1253D - Harmonious Graph Rating: 1700 Tags: constructive algorithms, dfs and similar, dsu, graphs, greedy, sortings Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given an undirected graph on vertices labeled from 1 to n, and we are allowed to add edges. The goal is to make the graph satisfy a very specific reachability constraint that depends on the natural ordering of vertices. The condition says...

CF 1248B - Grow The Tree

CF 1248B - Grow The Tree Rating: 900 Tags: greedy, math, sortings Solve time: 5m 32s Verified: no Solution Problem Understanding We are given a multiset of stick lengths, and we must arrange all of them into a polyline starting at the origin. Each stick becomes one segment of this polyline, and every segment must be axis-aligned, meaning it is either horizontal or vertical. The only structural constraint is that...

CF 1244E - Minimizing Difference

CF 1244E - Minimizing Difference Rating: 2000 Tags: binary search, constructive algorithms, greedy, sortings, ternary search, two pointers Solve time: 7m 31s Verified: no Solution Problem Understanding We are given a list of integers and a limited budget of unit operations. Each operation lets us pick a single element and move it by exactly one step, either up or down. The goal is not to make all numbers equal, but...

CF 1242B - 0-1 MST

CF 1242B - 0-1 MST Rating: 1900 Tags: dfs and similar, dsu, graphs, sortings Solve time: 5m 48s Verified: yes Solution Problem Understanding We are given a complete undirected graph on $n$ vertices. Every pair of vertices is connected, but edges come in only two possible weights: either 0 or 1. Among all $\binom{n}{2}$ edges, exactly $m$ of them have weight 1, and every other edge implicitly has weight 0....

CF 1238G - Adilbek and the Watering System

CF 1238G - Adilbek and the Watering System Rating: 2700 Tags: data structures, greedy, sortings Solve time: 3m 49s Verified: yes Solution Problem Understanding The system can only run if it never becomes empty, meaning at every minute it must contain at least one liter before consumption happens. It continuously drains one liter per minute for a total of m minutes, and its storage capacity is capped at c ....

CF 1238B - Kill `Em All

CF 1238B - Kill `Em All Rating: 1300 Tags: greedy, sortings Solve time: 2m 33s Verified: no Solution Problem Understanding The corridor can be seen as a number line where all monsters start strictly on the positive side. Each monster is a point on this line, and Ivan repeatedly performs an operation that chooses a center point and affects every monster depending on whether it lies to the left, at,...

Codeforces Global Round 5

Codeforces Global Round 5 Global | 9 problems | 3/9 verified | Difficulty 1000-3500 | 44m 41s # Problem Rating Tags Accepted Time ✓ A Balanced Rating Changes 1000 implementation, math 22,113 4m 41s ✓ B Balanced Tunnel 1300 data-structures, sortings, two-pointers 22,758 3m 15s ✓ C1 Balanced Removals (Easier) 1700 constructive-algorithms, geometry, greedy 6,300 3m 18s C2 Balanced Removals (Harder) 1900 binary-search, constructive-algorithms, divide-and-conquer 4,534 3m 53s D Balanced...

CF 1237C2 - Balanced Removals (Harder)

CF 1237C2 - Balanced Removals (Harder) Rating: 1900 Tags: binary search, constructive algorithms, divide and conquer, greedy, implementation, sortings Solve time: 3m 53s Verified: no Solution Problem Understanding We are given a set of points in three-dimensional space, and we must repeatedly delete them in pairs until nothing remains. The restriction is not about distance or parity, but about geometry of axis-aligned boxes. At any moment, we pick two remaining...

CF 1223E - Paint the Tree

CF 1223E - Paint the Tree Rating: 2100 Tags: dp, sortings, trees Solve time: 5m 17s Verified: yes Solution Problem Understanding We are given a tree where every edge has a weight. The task is to assign colors to vertices under a very specific rule: each vertex receives exactly $k$ colors, and any particular color can appear at most twice across the entire tree. This means every color effectively either...

CF 1221F - Choose a Square

CF 1221F - Choose a Square Rating: 2400 Tags: binary search, data structures, sortings Solve time: 3m 22s Verified: no Solution Something went wrong. If this issue persists please contact us through our help center at help.openai.com.

Codeforces Round 586 (Div. 1 + Div. 2)

Codeforces Round 586 (Div. 1 + Div. 2) Div. 1+2 | 7 problems | 4/7 verified | Difficulty 800-3400 | 26m 51s # Problem Rating Tags Accepted Time ✓ A Cards 800 implementation, sortings, strings 32,791 2m 11s ✓ B Multiplication Table 1300 math, number-theory 12,135 3m 19s ✓ C Substring Game in the Lesson 1300 games, greedy, strings 10,811 1m 34s ✓ D Alex and Julian 1900 bitmasks, math,...

CF 1220A - Cards

CF 1220A - Cards Rating: 800 Tags: implementation, sortings, strings Solve time: 2m 11s Verified: yes Solution Problem Understanding We are given a multiset of letters that originally came from writing several binary words, where each word is either the string "zero" representing digit 0 or "one" representing digit 1. These words were concatenated and then all letters were shuffled, so we lose all structure except the raw character counts....

COMPFEST 14 - Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred)

COMPFEST 14 - Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred) ICPC/IOI | 13 problems | 6/13 verified | Difficulty 800-2900 | 42m 39s # Problem Rating Tags Accepted Time ✓ A Accumulation of Dominoes 800 math 10,130 3m 15s ✓ B Basketball Together 1000 binary-search, greedy, sortings 28,235 1m 59s ✓ C Circular Mirror 2000 binary-search, combinatorics, geometry 1,947 5m 43s D Deducing Sortability 2900 binary-search, bitmasks, math 232...

Codeforces Round 587 (Div. 3)

Codeforces Round 587 (Div. 3) Div. 3 | 7 problems | 5/7 verified | Difficulty 800-2200 | 19m 54s # Problem Rating Tags Accepted Time ✓ A Prefixes 800 strings 19,549 2m 38s B Shooting 900 greedy, implementation, sortings 19,677 2m 12s ✓ C White Sheet 1700 geometry, math 10,357 2m 28s ✓ D Swords 1300 math 12,216 6m 10s E1 Numerical Sequence (easy version) 1900 binary-search, brute-force, math 3,730...

CF 1214E - Petya and Construction Set

CF 1214E - Petya and Construction Set Rating: 2000 Tags: constructive algorithms, graphs, math, sortings, trees Solve time: 2m 50s Verified: no Solution Problem Understanding We are asked to build a graph on $2n$ labeled vertices using exactly $2n-1$ edges. Since a connected graph with $2n$ vertices and $2n-1$ edges is necessarily a tree, the construction is really about designing a tree on these labeled nodes. The vertices come in...

Codeforces Round 582 (Div. 3)

Codeforces Round 582 (Div. 3) Div. 3 | 8 problems | 7/8 verified | Difficulty 900-2100 | 24m 43s # Problem Rating Tags Accepted Time ✓ A Chips Moving 900 math 25,602 1m 54s ✓ B Bad Prices 1100 data-structures, implementation 31,550 1m 20s ✓ C Book Reading 1200 math 19,621 1m 36s ✓ D1 Equalizing by Division (easy version) 1500 brute-force, implementation 12,077 3m 32s ✓ D2 Equalizing by...

CF 1209E2 - Rotate Columns (hard version)

CF 1209E2 - Rotate Columns (hard version) Rating: 2500 Tags: bitmasks, dp, greedy, sortings Solve time: 4m 14s Verified: no Solution Problem Understanding We are given a grid with a small number of rows and a potentially large number of columns. The only operation allowed is to take any single column and rotate it cyclically any number of times. After performing these rotations independently for each column, we look at...

Lyft Level 5 Challenge 2018 - Final Round (Open Div. 2)

Lyft Level 5 Challenge 2018 - Final Round (Open Div. 2) Div. 2 | 2 problems | 2/2 verified | Difficulty 800-1200 | 3m 21s # Problem Rating Tags Accepted Time ✓ A The King's Race 800 implementation, math 9,130 2m 24s ✓ B Taxi drivers and Lyft 1200 implementation, sortings 4,527 57s ✓

Educational Codeforces Round 56 (Rated for Div. 2)

Educational Codeforces Round 56 (Rated for Div. 2) Div. 2 | 7 problems | 4/7 verified | Difficulty 800-2400 | 38m 7s # Problem Rating Tags Accepted Time ✓ A Dice Rolling 800 math 18,356 6m 28s B Letters Rearranging 900 constructive-algorithms, greedy, sortings 17,700 6m 33s C Mishka and the Last Exam 1300 greedy 9,719 9m 12s D Beautiful Graph 1700 dfs-and-similar, graphs 11,323 3m 33s ✓ E Intersection...

CF 1093B - Letters Rearranging

CF 1093B - Letters Rearranging Rating: 900 Tags: constructive algorithms, greedy, sortings, strings Solve time: 6m 33s Verified: no Solution Problem Understanding We are given several independent strings made only of lowercase English letters. For each string, we are allowed to rearrange its characters in any order we want. After rearranging, we must decide whether it is possible to obtain a string that is not a palindrome, or report that...

Mail.Ru Cup 2018 Round 3

Mail.Ru Cup 2018 Round 3 Special | 8 problems | 7/8 verified | Difficulty 800-3200 | 29m 37s # Problem Rating Tags Accepted Time ✓ A Determine Line 800 implementation 7,307 3m 25s ✓ B Divide Candies 1600 math, number-theory 4,546 6m 37s ✓ C Pick Heroes 1700 greedy, implementation, interactive 2,579 5m D Decorate Apple Tree 1600 constructive-algorithms, dfs-and-similar, dp 6,719 2m 24s ✓ E Check Transcription 2100 brute-force,...

CF 1056C - Pick Heroes

CF 1056C - Pick Heroes Rating: 1700 Tags: greedy, implementation, interactive, sortings Solve time: 5m Verified: no Solution Problem Understanding Two players are building two equally sized teams by alternately taking heroes from a common pool of $2n$ candidates. Each hero has a fixed strength, and once taken it disappears from the game. On top of this, some heroes come in special pairs: if one hero of such a pair...

CF 1056D - Decorate Apple Tree

CF 1056D - Decorate Apple Tree Rating: 1600 Tags: constructive algorithms, dfs and similar, dp, graphs, greedy, sortings, trees Solve time: 2m 24s Verified: yes Solution Problem Understanding We are given a rooted tree, with node 1 fixed as the root. Only leaf nodes initially receive colors, and all other nodes are uncolored. A leaf, in this problem, is defined as a node whose subtree consists of only itself, which...

Codeforces Round 523 (Div. 2)

Codeforces Round 523 (Div. 2) Div. 2 | 6 problems | 3/6 verified | Difficulty 800-2600 | 30m 19s # Problem Rating Tags Accepted Time ✓ A Coins 800 greedy, implementation, math 24,100 1m 58s ✓ B Views Matter 1400 greedy, implementation, sortings 7,642 5m 49s ✓ C Multiplicity 1700 data-structures, dp, implementation 10,709 3m 7s D TV Shows 2000 data-structures, greedy, implementation 2,560 3m 52s E Politics 2600 flows,...

CF 1061D - TV Shows

CF 1061D - TV Shows Rating: 2000 Tags: data structures, greedy, implementation, sortings Solve time: 3m 52s Verified: no Solution Problem Understanding We are given a collection of time intervals, each representing a TV show that occupies a continuous range of minutes. The key constraint is that a single TV cannot be used to watch two shows whose intervals overlap in time. If one show is running from minute 2...

CF 1061B - Views Matter

CF 1061B - Views Matter Rating: 1400 Tags: greedy, implementation, sortings Solve time: 5m 49s Verified: yes Solution Problem Understanding We are given several vertical stacks of blocks placed side by side. Each position $i$ has a stack of height $a_i$. From above, the camera only cares whether a position is occupied or empty, so every column contributes exactly one visible cell as long as it has at least one...

Codeforces Round 521 (Div. 3)

Codeforces Round 521 (Div. 3) Div. 3 | 7 problems | 6/7 verified | Difficulty 800-2100 | 20m 23s # Problem Rating Tags Accepted Time ✓ A Frog Jumping 800 math 32,248 1m 58s ✓ B Disturbed People 1000 greedy 20,435 1m 58s ✓ C Good Array 1300 25,584 4m 23s D Cutting Out 1600 binary-search, sortings 10,474 2m 20s ✓ E Thematic Contests 1800 greedy, sortings 5,092 2m 57s...

CF 1077E - Thematic Contests

CF 1077E - Thematic Contests Rating: 1800 Tags: greedy, sortings Solve time: 2m 57s Verified: yes Solution Problem Understanding We are given a multiset of problems where each problem belongs to a topic. The same topic can appear many times. From this pool, we want to form several contests. Each contest must use only problems from a single topic, so it is homogeneous. Different contests must use different topics, so...

CF 1077D - Cutting Out

CF 1077D - Cutting Out Rating: 1600 Tags: binary search, sortings Solve time: 2m 20s Verified: yes Solution Problem Understanding We are given a multiset of integers, and we want to construct a pattern array of fixed length $k$. Once we choose this pattern, we repeatedly try to “extract” it from the original multiset: each extraction consumes one occurrence of every value in the pattern, and after each full extraction...

CF 1080F - Katya and Segments Sets

CF 1080F - Katya and Segments Sets Rating: 2400 Tags: data structures, interactive, sortings Solve time: 3m Verified: no Solution Problem Understanding We are given several collections of segments, where each collection corresponds to a set index from 1 to n. Inside a single set, there may be many segments, and each segment is a closed interval on the number line. The task revolves around answering queries about a range...

CF 1081D - Maximum Distance

CF 1081D - Maximum Distance Rating: 1800 Tags: dsu, graphs, shortest paths, sortings Solve time: 2m 31s Verified: yes Solution Problem Understanding We are given a connected weighted undirected graph where edges have costs, and a subset of vertices is marked as special. Between any two vertices, we define their “distance” in a nonstandard way: instead of summing weights along a path, we consider the maximum edge weight along the...

Educational Codeforces Round 55 (Rated for Div. 2)

Educational Codeforces Round 55 (Rated for Div. 2) Div. 2 | 7 problems | 4/7 verified | Difficulty 1200-2800 | 31m 12s # Problem Rating Tags Accepted Time ✓ A Vasya and Book 1200 implementation, math 9,273 4m 41s B Vova and Trophies 1600 greedy 8,028 4m 31s ✓ C Multi-Subject Competition 1600 greedy, sortings 6,133 2m 12s ✓ D Maximum Diameter Graph 1800 constructive-algorithms, graphs, implementation 4,089 6m 31s...

CF 1082C - Multi-Subject Competition

CF 1082C - Multi-Subject Competition Rating: 1600 Tags: greedy, sortings Solve time: 2m 12s Verified: yes Solution Problem Understanding Each candidate belongs to exactly one subject and brings a numeric contribution, which may be positive or negative. We are asked to choose a group of candidates under a structural constraint: after selection, we also choose some set of subjects, and for every chosen subject the number of selected candidates in...

Codeforces Round 525 (Div. 2)

Codeforces Round 525 (Div. 2) Div. 2 | 6 problems | 3/6 verified | Difficulty 800-2800 | 26m # Problem Rating Tags Accepted Time ✓ A Ehab and another construction problem 800 brute-force, constructive-algorithms 17,635 3m 4s B Ehab and subtraction 1000 implementation, sortings 13,584 2m 53s C Ehab and a 2-operation task 1400 constructive-algorithms, greedy, math 8,517 2m 56s ✓ D Ehab and another another xor problem 2000 bitmasks,...

CF 1088B - Ehab and subtraction

CF 1088B - Ehab and subtraction Rating: 1000 Tags: implementation, sortings Solve time: 2m 53s Verified: no Solution Problem Understanding We are repeatedly performing a global “level reduction” on an array. At each step, we look at all positive values currently present, identify the smallest among them, output that value, and then reduce every positive element by that same amount. Zeros remain unchanged and never contribute again. This process continues...

CF 1830C - Hyperregular Bracket Strings

CF 1830C - Hyperregular Bracket Strings Rating: 2400 Tags: combinatorics, greedy, hashing, math, number theory, sortings Solve time: 1m 14s Verified: no Solution Working

Codeforces Round 861 (Div. 2)

Codeforces Round 861 (Div. 2) Div. 2 | 7 problems | 4/7 verified | Difficulty 900-2800 | 18m 4s # Problem Rating Tags Accepted Time ✓ A Lucky Numbers 900 brute-force, implementation 20,611 2m 1s ✓ B Playing in a Casino 1200 math, sortings 29,642 1m 24s ✓ C Unlucky Numbers 1900 brute-force, dp, greedy 4,330 2m 28s D Petya, Petya, Petr, and Palindromes 2100 binary-search, brute-force, data-structures 2,706 2m...

CF 1773E - Easy Assembly

CF 1773E - Easy Assembly Rating: 1400 Tags: greedy, sortings Solve time: 2m 6s Verified: yes Solution Problem Understanding We are given several vertical stacks of uniquely numbered blocks. Each stack is ordered from top to bottom, and we are allowed to physically reorganize these blocks using two operations: we can cut a stack into two by taking a prefix or suffix segment and turning it into a new stack,...

Codeforces Round 831 (Div. 1 + Div. 2)

Codeforces Round 831 (Div. 1 + Div. 2) Div. 1+2 | 9 problems | 2/9 verified | Difficulty 800-3500 | 42m 43s # Problem Rating Tags Accepted Time ✓ A Factorise N+M 800 constructive-algorithms, number-theory 23,144 8m 2s B Jumbo Extra Cheese 2 800 geometry, greedy, sortings 14,352 6m 31s ✓ C Bricks and Bags 1400 constructive-algorithms, games, greedy 12,321 7m 28s D Knowledge Cards 1500 constructive-algorithms, data-structures 9,056 2m...

CF 1740G - Dangerous Laser Power

CF 1740G - Dangerous Laser Power Rating: 3100 Tags: constructive algorithms, dsu, sortings Solve time: 5m 10s Verified: no Solution Problem Understanding We are given an (n \times m) grid where each cell behaves like a directional device that routes a “laser” entering from one side to another side, while possibly increasing its speed. The routing rule depends on a binary configuration we must assign for each cell, and this...

CF 1740C - Bricks and Bags

CF 1740C - Bricks and Bags Rating: 1400 Tags: constructive algorithms, games, greedy, sortings Solve time: 7m 28s Verified: no Solution Problem Understanding We are given a multiset of integer weights representing bricks, and we must distribute every brick into one of three non-empty groups. After the distribution, an adversary chooses exactly one brick from each group, and they choose those three bricks in a way that makes a particular...

CF 1740B - Jumbo Extra Cheese 2

CF 1740B - Jumbo Extra Cheese 2 Rating: 800 Tags: geometry, greedy, sortings Solve time: 6m 31s Verified: yes Solution Problem Understanding We are given several test cases. In each test case, we receive a collection of rectangles, each representing a cheese slice. Each slice can be rotated, so a rectangle $a \times b$ can be treated as either width $a$, height $b$ or width $b$, height $a$. The task...

Codeforces Round 821 (Div. 2)

Codeforces Round 821 (Div. 2) Div. 2 | 6 problems | 1/6 verified | Difficulty 800-2700 | 22m 13s # Problem Rating Tags Accepted Time ✓ A Consecutive Sum 800 greedy, sortings 21,855 4m 30s ✓ B Rule of League 900 constructive-algorithms, math 21,072 3m 27s C Parity Shuffle Sorting 1300 constructive-algorithms, sortings 17,095 3m 23s D1 Zero-One (Easy Version) 1400 constructive-algorithms, greedy, math 15,030 3m 38s D2 Zero-One (Hard...

CF 1733A - Consecutive Sum

CF 1733A - Consecutive Sum Rating: 800 Tags: greedy, sortings Solve time: 4m 30s Verified: yes Solution Problem Understanding We are given an array of integers, and we are allowed to rearrange elements using a restricted swap operation. The restriction is that we can only swap positions whose indices share the same remainder when divided by a fixed number $k$. This partitions the array into $k$ independent index classes: positions...

CF 1733C - Parity Shuffle Sorting

CF 1733C - Parity Shuffle Sorting Rating: 1300 Tags: constructive algorithms, sortings Solve time: 3m 23s Verified: no Solution Problem Understanding We are given an array of integers and a peculiar operation that allows us to “transfer” values between two positions, but the direction of the transfer depends entirely on the parity relationship between the chosen pair. Each operation picks two indices l < r . If the sum of...

Codeforces Round 823 (Div. 2)

Codeforces Round 823 (Div. 2) Div. 2 | 6 problems | 3/6 verified | Difficulty 800-2700 | 20m 53s # Problem Rating Tags Accepted Time ✓ A Planets 800 data-structures, greedy, sortings 24,813 1m 20s ✓ B Meeting on the Line 1600 binary-search, geometry, greedy 17,252 1m 35s C Minimum Notation 1200 data-structures, greedy, math 17,933 1m 41s ✓ D Prefixes and Suffixes 2200 constructive-algorithms, strings, two-pointers 3,023 1m 58s...

CF 1730A - Planets

CF 1730A - Planets Rating: 800 Tags: data structures, greedy, sortings Solve time: 1m 20s Verified: yes Solution Problem Understanding We are given several independent test cases. In each test case there is a multiset of integers, where each integer represents an orbit label of a planet. Planets sharing the same value belong to the same orbit. We have two ways to destroy planets. One option removes a single planet...

Codeforces Round 820 (Div. 3)

Codeforces Round 820 (Div. 3) Div. 3 | 7 problems | 4/7 verified | Difficulty 800-2100 | 34m 16s # Problem Rating Tags Accepted Time ✓ A Two Elevators 800 math 45,887 5m 44s ✓ B Decode String 800 greedy, strings 32,472 6m 2s ✓ C Jumping on Tiles 1100 constructive-algorithms, strings 21,640 6m 38s D Friends and the Restaurant 1200 greedy, sortings, two-pointers 30,717 3m 52s ✓ E Guess...

CF 1729D - Friends and the Restaurant

CF 1729D - Friends and the Restaurant Rating: 1200 Tags: greedy, sortings, two pointers Solve time: 3m 52s Verified: yes Solution Problem Understanding We are given a collection of friends where each friend has two numbers: how much they intend to spend at a restaurant and how much money they actually have. The goal is to partition some of these friends into disjoint groups, where each group has at least...

Educational Codeforces Round 135 (Rated for Div. 2)

Educational Codeforces Round 135 (Rated for Div. 2) Div. 2 | 7 problems | 6/7 verified | Difficulty 800-3100 | 41m 34s # Problem Rating Tags Accepted Time ✓ A Colored Balls: Revisited 800 brute-force, greedy, implementation 25,449 6m 15s ✓ B Best Permutation 800 constructive-algorithms, greedy 20,671 1m 42s ✓ C Digital Logarithm 1400 data-structures, greedy, sortings 17,878 6m 16s ✓ D Letter Picking 1800 constructive-algorithms, dp, games 8,242...

CF 1728C - Digital Logarithm

CF 1728C - Digital Logarithm Rating: 1400 Tags: data structures, greedy, sortings Solve time: 6m 16s Verified: yes Solution Problem Understanding We are given two arrays of equal length. Each position contains a positive integer, and we are allowed to repeatedly replace a number by the number of digits it has in base 10. For example, 7 stays 1, 50 becomes 2, 1000 becomes 4, and applying the operation again...

CF 1728A - Colored Balls: Revisited

CF 1728A - Colored Balls: Revisited Rating: 800 Tags: brute force, greedy, implementation, sortings Solve time: 6m 15s Verified: yes Solution Problem Understanding We are given several test cases. In each test case, there are several colors of balls, and each color has a certain number of balls. The total number of balls across all colors is guaranteed to be odd. We repeatedly perform an operation where we pick two...

CF 1726G - A Certain Magical Party

CF 1726G - A Certain Magical Party Rating: 3300 Tags: combinatorics, data structures, greedy, sortings Solve time: 5m 44s Verified: no Solution Problem Understanding We are given a group of $n$ people, each starting with a happiness value $a_i$ and a binary personality flag $b_i$. We choose a permutation, which represents the order in which they speak. When a person speaks, they look at everyone else’s current happiness values and...

Codeforces Round 817 (Div. 4)

Codeforces Round 817 (Div. 4) Div. 4 | 7 problems | 3/7 verified | Difficulty 800-1700 | 21m 51s # Problem Rating Tags Accepted Time ✓ A Spell Check 800 implementation 65,585 2m 2s ✓ B Colourblindness 800 implementation 56,428 2m 14s ✓ C Word Game 800 data-structures, implementation 36,163 4m 33s D Line 1100 greedy, sortings 26,546 3m 13s E Counting Rectangles 1600 brute-force, data-structures, dp 13,352 4m 54s...

CF 1722D - Line

CF 1722D - Line Rating: 1100 Tags: greedy, sortings Solve time: 3m 13s Verified: no Solution Problem Understanding We are given a row of people, each either facing left or right. The contribution of a person depends on how many people lie in the direction they are looking. A person facing right contributes the number of people strictly to their right, while a person facing left contributes the number of...

CF 1721D - Maximum AND

CF 1721D - Maximum AND Rating: 1800 Tags: bitmasks, dfs and similar, divide and conquer, greedy, sortings Solve time: 3m 45s Verified: no Solution Problem Understanding We are given two arrays of equal length. One array, call it a , is fixed in place. The second array b can be permuted arbitrarily. After choosing a permutation of b , we pair elements by index and form a new array where...

Codeforces Round 815 (Div. 2)

Codeforces Round 815 (Div. 2) Div. 2 | 6 problems | 3/6 verified | Difficulty 800-2700 | 15m 22s # Problem Rating Tags Accepted Time ✓ A Burenka Plays with Fractions 900 math, number-theory 24,361 2m 8s ✓ B Interesting Sum 800 brute-force, data-structures, greedy 22,413 2m 18s ✓ C Corners 1200 greedy, implementation 18,229 3m 5s D1 Xor-Subsequence (easy version) 1800 bitmasks, brute-force, dp 6,709 2m 1s D2 Xor-Subsequence...

CF 1720B - Interesting Sum

CF 1720B - Interesting Sum Rating: 800 Tags: brute force, data structures, greedy, math, sortings Solve time: 2m 18s Verified: yes Solution Problem Understanding We are given an array of integers, and we are allowed to pick a single contiguous segment inside it, but not the whole array. Once we choose this segment, the array is conceptually split into two parts: the chosen segment and everything outside it. The score...

CF 1712C - Sort Zero

CF 1712C - Sort Zero Rating: 1100 Tags: greedy, sortings Solve time: 3m 47s Verified: no Solution Problem Understanding We are given several independent test cases, each consisting of an array of positive integers. In one move, we are allowed to pick a value x and simultaneously erase all occurrences of x in the array by turning them into zeros. The task is to apply this operation as few times...

CF 1658E - Gojou and Matrix Game

CF 1658E - Gojou and Matrix Game Rating: 2500 Tags: data structures, dp, games, hashing, implementation, math, number theory, sortings Solve time: 3m Verified: no Solution Problem Understanding The game is played on an $n \times n$ grid where each cell has a fixed value, and all values are distinct so there are no ties in scoring from identical weights. Marin always starts the game by choosing a specific starting...

CF 1656F - Parametric MST

CF 1656F - Parametric MST Rating: 2600 Tags: binary search, constructive algorithms, graphs, greedy, math, sortings Solve time: 4m 51s Verified: no Solution Problem Understanding We are given an array of integers, and we build a complete graph where every pair of vertices is connected. The weight of an edge between vertices $i$ and $j$ depends on a parameter $t$ and is defined as a linear function in $t$: it...

CF 1654F - Minimal String Xoration

CF 1654F - Minimal String Xoration Rating: 2800 Tags: bitmasks, data structures, divide and conquer, greedy, hashing, sortings, strings Solve time: 2m 42s Verified: yes Solution Problem Understanding We are given a string whose length is a power of two, indexed from 0 to $2^n - 1$. The key operation allowed is a global reindexing of the string using bitwise XOR with a fixed mask $j$. In other words, we...

CF 1583H - Omkar and Tours

CF 1583H - Omkar and Tours Rating: 3300 Tags: data structures, divide and conquer, sortings, trees Solve time: 6m 57s Verified: no Solution Problem Understanding We are given a tree of cities. Each city has a fixed value called enjoyment. Each road connects two cities and has two properties: a capacity and a toll. A group query gives a starting city and a number of vehicles. From the starting city,...

CF 1561A - Simply Strange Sort

CF 1561A - Simply Strange Sort Rating: 800 Tags: brute force, implementation, sortings Solve time: 2m 40s Verified: yes Solution Problem Understanding We are given a permutation, meaning an array containing every integer from 1 to n exactly once. The process repeatedly applies a deterministic “strange bubble pass” operation, but with a twist: odd-numbered rounds compare adjacent pairs starting from index 1, 3, 5, and even-numbered rounds start from index...

CF 1555E - Boring Segments

CF 1555E - Boring Segments Rating: 2100 Tags: data structures, sortings, trees, two pointers Solve time: 1m 46s Verified: yes Solution Problem Understanding We are given a set of weighted intervals on a number line from 1 to m. Each interval allows free movement between any two integer points inside it, which effectively means that once we pick a set of intervals, all points covered by overlapping intervals become connected...

CF 1552F - Telepanting

CF 1552F - Telepanting Rating: 2200 Tags: binary search, data structures, dp, sortings Solve time: 5m 13s Verified: no Solution Problem Understanding We are simulating a point moving on a number line. The point starts at position 0 and moves strictly to the right at unit speed, so without any interruptions it would simply take $t$ seconds to reach position $t$. The complication comes from special “portals” placed at distinct...

CF 1552A - Subsequence Permutation

CF 1552A - Subsequence Permutation Rating: 800 Tags: sortings, strings Solve time: 6m 22s Verified: yes Solution Problem Understanding We are given a string made of lowercase letters. In one move, we are allowed to pick exactly one subset of positions, take the characters at those positions, and rearrange only those chosen characters arbitrarily while keeping all other characters fixed in their original places. The goal is to make the...

CF 1551C - Interesting Story

CF 1551C - Interesting Story Rating: 1500 Tags: greedy, sortings, strings Solve time: 4m 47s Verified: yes Solution Problem Understanding We are given several independent test cases. In each test case, we receive a list of words, and we want to select as many of these words as possible so that the selected subset satisfies a specific imbalance condition. The condition is evaluated by looking at letter frequencies across all...

CF 1550D - Excellent Arrays

CF 1550D - Excellent Arrays Rating: 2300 Tags: binary search, combinatorics, constructive algorithms, implementation, math, sortings, two pointers Solve time: 6m 20s Verified: no Solution Problem Understanding We are given an array of length $n$, and each position $i$ must store an integer $a_i$ within a fixed interval $[l, r]$. Two constraints define what makes a valid configuration interesting. First, the array must be “good”, meaning no position is allowed...

CF 1547E - Air Conditioners

CF 1547E - Air Conditioners Rating: 1500 Tags: data structures, dp, implementation, shortest paths, sortings, two pointers Solve time: 7m 45s Verified: no Solution Problem Understanding We are given a one-dimensional strip of length $n$. Some positions on this strip contain air conditioners, each fixed at a known coordinate and each producing its own base temperature. Every other cell inherits a temperature determined by its distance to all air conditioners:...

Codeforces Global Round 15

Codeforces Global Round 15 Global | 9 problems | 4/9 verified | Difficulty 800-3400 | 40m 13s # Problem Rating Tags Accepted Time ✓ A Subsequence Permutation 800 sortings, strings 25,328 6m 22s ✓ B Running for Gold 1500 combinatorics, graphs, greedy 16,929 1m 43s ✓ C Maximize the Intersections 1800 combinatorics, constructive-algorithms, geometry 6,286 7m 19s D Array Differentiation 1800 bitmasks, brute-force, constructive-algorithms 7,886 5m 22s E Colors and...

Kotlin Heroes: Practice 7

Kotlin Heroes: Practice 7 Kotlin | 6 problems | 3/6 verified | Difficulty - | 19m 14s # Problem Rating Tags Accepted Time ✓ A A+B (Trial Problem) *special 1,150 2m 54s ✓ B Frog Jumping *special, math 829 2m 47s ✓ C Uniform String *special, implementation 641 4m 20s D Teams Forming *special, sortings 590 1m 21s ✓ E Good Array *special 392 3m 28s F Prefixes and Suffixes...

Codeforces Round 740 (Div. 2, based on VK Cup 2021 - Final (Engine))

Codeforces Round 740 (Div. 2, based on VK Cup 2021 - Final (Engine)) Div. 2 | 3 problems | 2/3 verified | Difficulty 800-1700 | 10m 18s # Problem Rating Tags Accepted Time ✓ A Simply Strange Sort 800 brute-force, implementation, sortings 17,167 2m 40s ✓ C Deep Down Below 1300 binary-search, greedy, sortings 21,396 1m 39s ✓ D1 Up the Strip (simplified version) 1700 brute-force, data-structures, dp 6,113 5m...

CF 1271D - Portals Rating: 2100 Tags: data structures, dp, greedy, implementation, sortings Model: gpt-5-3-mini Solve time: 3m 21s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2d91d1-6be8-83ec-9b8e-ca8089c0a5e8 Solution Problem Understanding We are given a fixed sequence of castles that must be conquered strictly in order from 1 to n. To conquer castle i, the army must currently have at least a_i warriors. After conquering it, the army does not lose strength, and...

CF 1320A - Journey Planning Rating: 1400 Tags: data structures, dp, greedy, math, sortings Model: gpt-5-5 Solve time: 4m 27s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2de6ec-99fc-83ec-9276-106005ae8eca Solution Problem Understanding We are given a line of cities, each with an index from left to right and an associated beauty value. We need to choose a sequence of cities to visit such that indices strictly increase. The key restriction is that consecutive...

CF 1354F - Summoning Minions Rating: 2500 Tags: constructive algorithms, dp, flows, graph matchings, greedy, sortings Model: gpt-5-3-mini Solve time: 7m 51s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e3235-4d04-83ec-969f-ae99dbac5d4a Solution Problem Understanding We are given a collection of minions, each with an intrinsic strength and a “buffing power”. When a minion is summoned, it contributes its base strength, but it also permanently increases the power of every minion that has already...

CF 1316E - Team Building Rating: 2300 Tags: bitmasks, dp, greedy, sortings Model: gpt-5-3-mini Solve time: 2m 52s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2de5ba-74c8-83ec-b78e-8c873f6a8ba6 Solution Problem Understanding We are asked to build a club structure from a pool of $n$ people. Each person can either become a player assigned to exactly one of $p$ distinct positions, or become part of an audience group of size exactly $k$. Nobody can be...

CF 1294B - Collecting Packages Rating: 1200 Tags: implementation, sortings Model: gpt-5-5 Solve time: 4m 20s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2dc44f-5540-83ec-8334-913517db904d Solution Problem Understanding A robot starts at the origin of a grid and can only move in two directions: right or up. Each package is located at a distinct grid coordinate with non-negative integer values. The robot must visit all package locations starting from the origin, and it...

CF 1360B - Honest Coach Rating: 800 Tags: greedy, sortings Model: gpt-5-3-mini Solve time: 3m 38s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e3de0-0334-83ec-9ad2-5a24d5b4b9f9 Solution Problem Understanding We are given several independent test cases. In each case we receive a list of athlete strengths, and we must divide the athletes into two non-empty groups so that one group contributes its maximum value and the other contributes its minimum value, and the absolute...

CF 1355E - Restorer Distance Rating: 2100 Tags: binary search, greedy, math, sortings, ternary search Model: gpt-5-3-mini Solve time: 2m 28s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e330b-04a4-83ec-b54e-ca818cfda1d4 Solution Problem Understanding We are given a row of pillars, each with an initial height. The goal is to transform these heights so that every pillar ends up at the same final height. We are allowed to either add bricks, remove bricks, or...

CF 1379D - New Passenger Trams Rating: 2300 Tags: binary search, brute force, data structures, sortings, two pointers Model: gpt-5-3-mini Solve time: 4m 36s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e6460-6b3c-83ec-8292-9e3f9f8e4c60 Solution Problem Understanding We are given a full-day timetable where freight trains already depart at fixed times. The day is cyclic with h hours and m minutes per hour, so every train time can be treated as a point on...

CF 1358B - Maria Breaks the Self-isolation Rating: 1000 Tags: greedy, sortings Model: gpt-5-3-mini Solve time: 3m 9s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e3899-7340-83ec-9d2b-cbafc7af3f4e Solution Problem Understanding We are given a collection of grannies, each with a personal requirement about crowd size. Maria starts alone in a courtyard and wants to gradually invite some of them. Each granny has a threshold $a_i$, meaning she will only agree to enter if,...

CF 1334B - Middle Class Rating: 1100 Tags: greedy, sortings Model: gpt-5-5 Solve time: 2m 30s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e0b1f-105c-83ec-b139-a797acfe317f Solution Problem Understanding We are given a group of people, each with some amount of money. A “wealthy” person is defined as someone whose final amount of money is at least a threshold value $x$. We are allowed to perform an operation any number of times. Each operation...

CF 1369C - RationalLee Rating: 1400 Tags: greedy, math, sortings, two pointers Model: gpt-5-5 Solve time: 2m 35s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e511f-c224-83ec-b707-723e5d51dfb6 Solution Problem Understanding We are given a collection of integers that must be split into groups, where each group is assigned to a different friend. Each friend receives exactly a fixed number of integers, and every integer must be used exactly once. The satisfaction of a...

CF 1333F - Kate and imperfection Rating: 2200 Tags: greedy, implementation, math, number theory, sortings, two pointers Model: gpt-5-3-mini Solve time: 2m 21s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e0a51-1884-83ec-a398-ce3d30119865 Solution Problem Understanding We are given the numbers from 1 to n. We must choose subsets of these numbers and measure how “bad” a subset is. The badness is defined by looking at every pair inside the subset, computing their gcd,...

CF 1353D - Constructing the Array Rating: 1600 Tags: constructive algorithms, data structures, sortings Model: gpt-5-3-mini Solve time: 5m 14s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e2f09-bb38-83ec-8c0b-26a2dc3eab95 Solution Problem Understanding We start with an array of length n filled with zeros. We repeatedly “fill” the array in n steps. At each step, we look at the current zero-filled segments and pick one segment to place the next number. The rule for...

CF 1374D - Zero Remainder Array Rating: 1400 Tags: math, sortings, two pointers Model: gpt-5-5 Solve time: 1m 42s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e5b90-5328-83ec-aa40-c68158cde90a Solution Problem Understanding We are given an array of positive integers. We can perform a sequence of moves, and each move advances a global counter x starting from zero. At each step we either skip or “use” the current value of x on exactly one...

CF 1311F - Moving Points Rating: 1900 Tags: data structures, divide and conquer, implementation, sortings Model: gpt-5-3-mini Solve time: 1m 50s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2dddac-65f8-83ec-bdff-9c933b0e2972 Solution Problem Understanding We are given a set of points on a number line. Each point starts at some integer position and moves forever in time, each with its own constant velocity. If we pick any two points, their distance changes over time...

CF 1282C - Petya and Exam Rating: 1800 Tags: greedy, sortings, two pointers Model: gpt-5-3-mini Solve time: 2m 55s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2da601-1174-83ec-845c-92c2dc74892b Solution Problem Understanding Each test case describes an exam where problems arrive with deadlines and take different amounts of time depending on whether they are easy or hard. Petya processes problems sequentially starting from time zero, choosing an order, and may stop at any integer...

CF 1336A - Linova and Kingdom Rating: 1600 Tags: dfs and similar, dp, greedy, sortings, trees Model: gpt-5-3-mini Solve time: 2m 38s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e1063-f548-83ec-9101-e12e782ec1b0 Solution Problem Understanding We are given a tree rooted at city 1. Each city is either selected as an industrial city or a tourism city, with exactly $k$ cities chosen as industrial. Every industrial city sends one envoy to the capital. That...

CF 1300B - Assigning to Classes Rating: 1000 Tags: greedy, implementation, sortings Model: gpt-5-3-mini Solve time: 8m 11s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2dcf8e-8efc-83ec-9652-050fd6ce2fec Solution Problem Understanding We are given an array of size $2n$, representing skill levels of students. The task is to split these students into two groups, each group containing an odd number of students, with every student assigned to exactly one group. For any group, we...

CF 1272A - Three Friends Rating: 900 Tags: brute force, greedy, math, sortings Model: gpt-5-3-mini Solve time: 7m 25s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2d9442-10c4-83ec-931d-e497b4ec06e0 Solution Problem Understanding Three friends sit on a number line at positions $a$, $b$, and $c$. In one move, each friend can shift by at most one unit left, one unit right, or stay where they are. After exactly one simultaneous move, we look at...

CF 1322B - Present Rating: 2100 Tags: binary search, bitmasks, constructive algorithms, data structures, math, sortings Model: gpt-5-3-mini Solve time: 1m 28s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2deae4-fc9c-83ec-aeba-66f8cbbf4563 Solution Problem Understanding We are given an array of integers, and we consider every unordered pair of distinct elements. For each pair, we compute their sum. After collecting all these pairwise sums, instead of summing or minimizing them, we combine them using...

CF 1342D - Multiple Testcases Rating: 1900 Tags: binary search, constructive algorithms, data structures, greedy, sortings, two pointers Model: gpt-5-3-mini Solve time: 8m 41s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e1bc3-6528-83ec-be3b-9d57dd5c8d13 Solution Problem Understanding We are given a collection of arrays, but the actual contents of these arrays do not matter at all. Each array is characterized only by its size. Our task is to pack all these arrays into several...

CF 1381C - Mastermind Rating: 2500 Tags: constructive algorithms, graph matchings, greedy, implementation, sortings, two pointers Model: gpt-5-3-mini Solve time: 4m 37s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e6d9f-55a8-83ec-97be-24bac196aec3 Solution Problem Understanding We are given a sequence b of length n , representing Bob’s guess, and two integers x and y describing how this guess overlaps with an unknown hidden sequence a of the same length. The hidden sequence uses colors...

CF 1311B - WeirdSort Rating: 1200 Tags: dfs and similar, sortings Model: gpt-5-3-mini Solve time: 1m 37s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2ddd1f-d1b0-83ec-a3a6-913f2c755799 Solution Problem Understanding We are given an array of integers and a limited set of “swap permissions”. Each permission corresponds to a position i , meaning we are allowed to swap the pair (a[i], a[i+1]) . Each such swap can be used arbitrarily many times, so effectively...

CF 1369E - DeadLee Rating: 2400 Tags: data structures, dfs and similar, greedy, implementation, sortings Model: gpt-5-3-mini Solve time: 3m 48s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e507d-5c50-83ec-98a0-7e3f660bf5f5 Solution Problem Understanding Each friend is connected to exactly two food types, and each food type has a limited stock of plates. When a friend is called, they attempt to consume one plate from each of their two preferred types. If at least...

CF 1257C - Dominated Subarray

CF 1257C - Dominated Subarray Rating: 1200 Tags: greedy, implementation, sortings, strings, two pointers Solve time: 4m 19s Verified: yes Solution Problem Understanding We are given several arrays, and for each one we need to find the shortest contiguous segment that has a strict majority element. A segment is considered valid if it contains at least two elements and there exists a value whose frequency inside the segment is strictly...

CF 1257D - Yet Another Monster Killing Problem

CF 1257D - Yet Another Monster Killing Problem Rating: 1700 Tags: binary search, data structures, dp, greedy, sortings, two pointers Solve time: 3m 35s Verified: yes Solution Problem Understanding We are given a sequence of monsters that must be defeated strictly from left to right. Each monster has a required strength threshold, and none can be skipped or reordered. We also have a pool of heroes. Each hero has a...

Codeforces Round 594 (Div. 2)

Codeforces Round 594 (Div. 2) Div. 2 | 3 problems | 1/3 verified | Difficulty 900-2000 | 16m 8s # Problem Rating Tags Accepted Time ✓ A Integer Points 1000 geometry, math 15,104 3m 37s ✓ B Grow The Tree 900 greedy, math, sortings 18,015 5m 32s D1 The World Is Just a Programming Task (Easy Version) 2000 brute-force, dp, greedy 2,521 6m 59s

Educational Codeforces Round 75 (Rated for Div. 2)

Educational Codeforces Round 75 (Rated for Div. 2) Div. 2 | 7 problems | 1/7 verified | Difficulty 1000-2500 | 28m # Problem Rating Tags Accepted Time ✓ A Broken Keyboard 1000 brute-force, strings, two-pointers 21,550 5m 7s B Binary Palindromes 1400 greedy, strings 11,617 2m 36s C Minimize The Integer 1600 greedy, two-pointers 14,331 2m 40s D Salary Changing 1900 binary-search, greedy, sortings 6,465 4m 31s ✓ E1 Voting...

CF 1251D - Salary Changing

CF 1251D - Salary Changing Rating: 1900 Tags: binary search, greedy, sortings Solve time: 4m 31s Verified: yes Solution Problem Understanding We are given several independent scenarios. In each scenario, there are an odd number of employees, and each employee has a salary interval from which their final salary must be chosen. We are also given a total budget that is guaranteed to be large enough to pay everyone their...

CF 1249D2 - Too Many Segments (hard version)

CF 1249D2 - Too Many Segments (hard version) Rating: 1800 Tags: data structures, greedy, sortings Solve time: 8m 52s Verified: no Solution Problem Understanding We are given a collection of integer segments on a number line. Each segment covers every integer point between its endpoints. A point becomes problematic if it is covered by more than $k$ segments at the same time. Our task is to delete as few segments...

CF 1237B - Balanced Tunnel

CF 1237B - Balanced Tunnel Rating: 1300 Tags: data structures, sortings, two pointers Solve time: 3m 15s Verified: yes Solution Problem Understanding We are given a timeline of cars entering a tunnel and a separate timeline of the same cars exiting it. Every car appears exactly once in each list, so both sequences are permutations of the same set of identifiers. Inside the tunnel, overtaking is only detectable indirectly. A...

CF 1213G - Path Queries

CF 1213G - Path Queries Rating: 1800 Tags: divide and conquer, dsu, graphs, sortings, trees Solve time: 4m 31s Verified: yes Solution Problem Understanding We are given a weighted tree where every edge has a cost, and we are asked multiple questions about how “expensive” paths between pairs of vertices can be. For any two vertices $u$ and $v$, there is exactly one simple path between them because the graph...

Codeforces Round 536 (Div. 2)

Codeforces Round 536 (Div. 2) Div. 2 | 5 problems | 5/5 verified | Difficulty 800-2400 | 16m 55s # Problem Rating Tags Accepted Time ✓ A Lunar New Year and Cross Counting 800 implementation 12,864 4m 34s ✓ C Lunar New Year and Number Division 900 greedy, implementation, math 15,906 1m 15s ✓ D Lunar New Year and a Wander 1500 data-structures, dfs-and-similar, graphs 19,644 4m 40s ✓ E...

CF 1206A - Choose Two Numbers

CF 1206A - Choose Two Numbers Rating: 800 Tags: math, sortings Solve time: 11m 11s Verified: no Solution Problem Understanding We are given two collections of positive integers. One collection represents the possible values we can pick as the first number, and the second collection represents the possible values we can pick as the second number. After choosing one value from each collection, we form their sum. The constraint is...

Codeforces Round 580 (Div. 2)

Codeforces Round 580 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-900 | Time: 12m 54s Problem Name Rating Tags Solve Time Verified A Choose Two Numbers 800 math, sortings 11m 11s ✗ B Make Product Equal One 900 dp, implementation 1m 43s ✓

Codeforces Round 579 (Div. 3)

Codeforces Round 579 (Div. 3) Type: Div. 3 | Problems: 8 | Verified: 8/8 | Rating range: 1000-2300 | Time: 28m 41s Problem Name Rating Tags Solve Time Verified A Circle of Students 1000 implementation 7m ✓ B Equal Rectangles 1200 greedy, math 1m 55s ✓ C Common Divisors 1300 implementation, math 1m 39s ✓ D1 Remove the Substring (easy version) 1600 greedy, implementation 4m 44s ✓ D2 Remove the...

CF 1201C - Maximum Median

CF 1201C - Maximum Median Rating: 1400 Tags: binary search, greedy, math, sortings Solve time: 3m 59s Verified: yes Solution Problem Understanding We are given a list of numbers and allowed to repeatedly increase any single element by one. Each such increment has a cost of one operation, and we have a total budget of at most $k$ operations. The goal is not to maximize the sum or any global...

Codeforces Round 576 (Div. 1)

Codeforces Round 576 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 4/6 | Rating range: 1600-2900 | Time: 23m 39s Problem Name Rating Tags Solve Time Verified A MP3 1600 sortings, two-pointers 2m 46s ✓ B Welfare State 1600 binary-search, brute-force, data-structures 3m 24s ✓ C Matching vs Independent Set 2000 constructive-algorithms, graphs, greedy 6m 44s ✗ D Rectangle Painting 1 2300 dp 4m 34s ✓ E Rectangle...

CF 1198A - MP3

CF 1198A - MP3 Rating: 1600 Tags: sortings, two pointers Solve time: 2m 46s Verified: yes Solution Problem Understanding We are given a sequence of sound intensities, each a non-negative integer. Think of it as a time series of sampled audio amplitudes. The file is stored using a fixed number of bits per value, and that bit cost depends only on how many distinct values appear after we possibly modify...

CF 1198C - Matching vs Independent Set

CF 1198C - Matching vs Independent Set Rating: 2000 Tags: constructive algorithms, graphs, greedy, sortings Solve time: 6m 44s Verified: no Solution Problem Understanding We are given several undirected graphs, each with exactly $3n$ vertices. For each graph, we must construct one of two specific structures of size $n$: either a matching consisting of $n$ edges, or an independent set consisting of $n$ vertices. If neither structure exists, we must...

CF 1198B - Welfare State

CF 1198B - Welfare State Rating: 1600 Tags: binary search, brute force, data structures, sortings Solve time: 3m 24s Verified: yes Solution Problem Understanding We are maintaining a dynamic list of balances for a fixed set of citizens. Initially, each citizen has a known amount of money. Then a sequence of events modifies these balances in two different ways. The first type of event directly sets one specific citizen’s balance...

Educational Codeforces Round 69 (Rated for Div. 2)

Educational Codeforces Round 69 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 900-2700 | Time: 29m 56s Problem Name Rating Tags Solve Time Verified A DIY Wooden Ladder 900 greedy, math, sortings 5m 53s ✓ B Pillars 1000 greedy, implementation 4m 34s ✓ C Array Splitting 1400 greedy, sortings 1m 27s ✓ D Yet Another Subarray Problem 1900 dp, greedy, math 4m...

CF 1197E - Culture Code

CF 1197E - Culture Code Rating: 2300 Tags: binary search, combinatorics, data structures, dp, shortest paths, sortings Solve time: 7m 53s Verified: no Solution Problem Understanding We are given a collection of matryoshka dolls. Each doll has two parameters: an outer volume and an inner empty volume. A doll can be placed inside another if the outer volume of the inner doll does not exceed the inner volume of the...

CF 1197A - DIY Wooden Ladder

CF 1197A - DIY Wooden Ladder Rating: 900 Tags: greedy, math, sortings Solve time: 5m 53s Verified: yes Solution Problem Understanding We are given several independent sets of wooden planks, where each plank has a fixed length and cannot be cut. From each set, we want to assemble a structure called a ladder with as many steps as possible. A k-step ladder is formed by selecting exactly k + 2...

CF 1196F - K-th Path

CF 1196F - K-th Path Rating: 2200 Tags: brute force, constructive algorithms, shortest paths, sortings Solve time: 4m 44s Verified: yes Solution Problem Understanding We are given an undirected weighted graph where every pair of vertices is connected by at least one path. Between any two vertices, there is a well-defined shortest path length. If we take every unordered pair of distinct vertices and compute the shortest distance between them,...

CF 1195F - Geometers Anonymous Club

CF 1195F - Geometers Anonymous Club Rating: 2500 Tags: data structures, geometry, math, sortings Solve time: 8m 43s Verified: yes Solution Problem Understanding We are given a sequence of convex polygons, and each polygon is described by its vertices in counterclockwise order. For any query interval $[l, r]$, we conceptually take all polygons in that range and compute their Minkowski sum. The task is not to construct the resulting polygon,...

CF 1194E - Count The Rectangles

CF 1194E - Count The Rectangles Rating: 2200 Tags: bitmasks, brute force, data structures, geometry, sortings Solve time: 4m 34s Verified: yes Solution Problem Understanding We are given a collection of axis-aligned line segments in the plane. Each segment is either perfectly horizontal or perfectly vertical. Horizontal segments never overlap with other horizontal segments, and the same is true for vertical segments. Intersections only happen between a horizontal and a...

CF 1190D - Tokitsukaze and Strange Rectangle

CF 1190D - Tokitsukaze and Strange Rectangle Rating: 2000 Tags: data structures, divide and conquer, sortings, two pointers Solve time: 8m 42s Verified: no Solution Problem Understanding We are given a set of points in the plane, and we are allowed to choose a special kind of region: a vertical strip between two x-coordinates, say between l and r, but open on the sides, combined with a horizontal threshold a...

CF 1187D - Subarray Sorting

CF 1187D - Subarray Sorting Rating: 2400 Tags: data structures, sortings Solve time: 12m 26s Verified: no Solution Problem Understanding We are given two arrays of equal length and allowed to repeatedly pick any contiguous segment of the first array and sort only that segment in non-decreasing order. After any number of such operations, we want to know whether we can transform the initial array into the target array exactly....

Codeforces Round 568 (Div. 2)

Codeforces Round 568 (Div. 2) Type: Div. 2 | Problems: 9 | Verified: 7/9 | Rating range: 800-2600 | Time: 43m 5s Problem Name Rating Tags Solve Time Verified A Ropewalkers 800 math 10m 56s ✓ B Email from Polycarp 1200 implementation, strings 1m 26s ✓ C1 Exam in BerSU (easy version) 1200 greedy, sortings 1m 40s ✓ C2 Exam in BerSU (hard version) 1700 brute-force, data-structures, greedy 6m 6s...

Codeforces Round 455 (Div. 2)

Codeforces Round 455 (Div. 2) Div. 2 | 6 problems | 6/6 verified | Difficulty 1000-2500 | 37m 14s # Problem Rating Tags Accepted Time ✓ A Generate Login 1000 brute-force, greedy, sortings 10,356 11m 29s ✓ B Segments 1300 constructive-algorithms, math 6,761 7m 55s ✓ C Python Indentation 1800 dp 5,486 3m ✓ D Colorful Points 2100 data-structures, greedy, implementation 2,105 5m 10s ✓ E Coprocessor 1900 dfs-and-similar, dp,...

CF 1184B1 - The Doctor Meets Vader (Easy)

CF 1184B1 - The Doctor Meets Vader (Easy) Rating: 1400 Tags: binary search, sortings Solve time: 5m 28s Verified: yes Solution Problem Understanding Each spaceship has an attack power. Each empire base has a defense value and a gold amount. A spaceship can destroy every base whose defense is not greater than the spaceship's attack power. Since destroying a base gives all of its gold, the answer for a spaceship...

CF 1183G - Candy Box (hard version)

CF 1183G - Candy Box (hard version) Rating: 2000 Tags: greedy, implementation, sortings Solve time: 4m 31s Verified: yes Solution Problem Understanding Each candy belongs to a type. For every type, we know how many candies of that type exist, and among those candies how many have f = 1 . We want to build a gift by selecting some candies. If we take candies from several types, then the...

CF 1183F - Topforces Strikes Back

CF 1183F - Topforces Strikes Back Rating: 2100 Tags: brute force, math, sortings Solve time: 4m 25s Verified: yes Solution Problem Understanding We are given several independent datasets. In each dataset there is a multiset of positive integers, where each integer represents the “value” of a problem. From this pool, we must pick at most three values to maximize their sum, but with a strong restriction: no chosen value is...

CF 1183D - Candy Box (easy version)

CF 1183D - Candy Box (easy version) Rating: 1400 Tags: greedy, sortings Solve time: 2m 22s Verified: yes Solution Problem Understanding We are given several independent candy collections. Each collection is just a multiset of integers, where each integer represents a candy type. From each collection, we want to build a single “gift” by selecting some candies. The restriction is on how many candies of each type we are allowed...

CF 1181E2 - A Story of One Country (Hard)

CF 1181E2 - A Story of One Country (Hard) Rating: 3000 Tags: brute force, greedy, sortings Solve time: 2m 39s Verified: yes Solution Problem Understanding We are given a set of axis-aligned rectangles that represent “castles”. These rectangles do not overlap in area, although they may share boundaries or corners. The claim is that these castles come from an earlier history where each castle belonged to its own country, and...

CF 1181D - Irrigation

CF 1181D - Irrigation Rating: 2200 Tags: binary search, data structures, implementation, sortings, trees, two pointers Solve time: 3m 36s Verified: yes Solution Problem Understanding We are given a sequence of past assignments where each of $m$ cities has hosted an event some number of times. After these first $n$ years, a deterministic rule takes over: in every future year, the city that has hosted the fewest events so far...

CF 1176D - Recover it!

CF 1176D - Recover it! Rating: 1800 Tags: dfs and similar, graphs, greedy, number theory, sortings Solve time: 9m 59s Verified: no Solution Problem Understanding We are given an unknown array of integers. Each original value is between 2 and 200000. From this hidden array, a second array is produced by expanding every element into two values and then shuffling everything. Our task is to reconstruct any original array that...

CF 1175D - Array Splitting

CF 1175D - Array Splitting Rating: 1900 Tags: greedy, sortings Solve time: 3m 15s Verified: yes Solution Problem Understanding We are given a sequence of numbers and we must cut it into exactly $k$ consecutive parts, where each element belongs to exactly one part and parts preserve order. Once the partition is fixed, every element gets a label equal to the index of the segment it lands in. The total...

Codeforces Round 563 (Div. 2)

Codeforces Round 563 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 1000-2500 | Time: 24m 56s Problem Name Rating Tags Solve Time Verified A Ehab Fails to Be Thanos 1000 constructive-algorithms, greedy, sortings 2m 41s ✗ B Ehab Is an Odd Person 1200 sortings 1m 33s ✓ C Ehab and a Special Coloring Problem 1300 constructive-algorithms, number-theory 2m 22s ✓ D Ehab and the...

CF 1174A - Ehab Fails to Be Thanos

CF 1174A - Ehab Fails to Be Thanos Rating: 1000 Tags: constructive algorithms, greedy, sortings Solve time: 2m 41s Verified: no Solution Problem Understanding We are given a multiset of integers of size exactly twice some number n. The task is to rearrange these values into a new order such that if we split the reordered array into two consecutive halves of length n, the sum of the left half...

CF 1165B - Polycarp Training

CF 1165B - Polycarp Training Rating: 1000 Tags: data structures, greedy, sortings Solve time: 1m 25s Verified: no Solution Problem Understanding We are given a list of contests, each with a certain number of problems. Polycarp trains day by day, and on day $k$, he must pick exactly one unused contest and solve exactly $k$ problems from it. A contest can be partially used: if it has more problems than...

CF 1102E - Monotonic Renumeration

CF 1102E - Monotonic Renumeration Rating: 1700 Tags: combinatorics, sortings Solve time: 5m 21s Verified: no Solution Problem Understanding We are given a sequence of integers, and we want to assign another sequence of integers of the same length, starting from zero, with very specific structure rules. First, every position that contains the same value in the original array must also receive the same value in the constructed array. So...

CF 1102B - Array K-Coloring

CF 1102B - Array K-Coloring Rating: 1400 Tags: greedy, sortings Solve time: 7m 32s Verified: no Solution Problem Understanding We are given a sequence of integers and asked to assign each position one of k labels, which we will call colors. Every position must receive exactly one color. At the same time, every color from 1 to k must appear at least once among all positions. There is one additional...

Educational Codeforces Round 58 (Rated for Div. 2)

Educational Codeforces Round 58 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 5/7 | Rating range: 1000-2400 | Time: 33m 51s Problem Name Rating Tags Solve Time Verified A Minimum Integer 1000 math 5m 4s ✓ B Accordion 1300 greedy, implementation 1m 13s ✓ C Division and Union 1500 sortings 6m 57s ✗ D GCD Counting 2000 data-structures, dfs-and-similar, dp 4m 55s ✓ E Polycarp's New...

CF 1101C - Division and Union

CF 1101C - Division and Union Rating: 1500 Tags: sortings Solve time: 6m 57s Verified: no Solution Problem Understanding We are given several independent test cases. Each test case provides a collection of closed segments on a number line. The task is to assign every segment to one of two groups such that no segment in one group overlaps with any segment in the other group. Overlap here means the...

CF 1256E - Yet Another Division Into Teams Rating: 2000 Tags: dp, greedy, sortings Model: gpt-5-5 Solve time: 2m 26s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2d777a-ed08-83ec-a2e0-aecc284a77b2 Solution Problem Understanding We are given a list of student skill values, and we must split these students into groups such that every student belongs to exactly one group, and every group has at least three students. For each group, its cost is defined...

Codeforces Round 527 (Div. 3)

Codeforces Round 527 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 4/7 | Rating range: 800-2200 | Time: 36m 33s Problem Name Rating Tags Solve Time Verified A Uniform String 800 implementation 9m 46s ✗ B Teams Forming 800 sortings 2m 51s ✓ C Prefixes and Suffixes 1700 strings 2m 57s ✓ D1 Great Vova Wall (Version 1) 2200 greedy, implementation, math 4m 20s ✓ D2 Great Vova...

CF 1092B - Teams Forming

CF 1092B - Teams Forming Rating: 800 Tags: sortings Solve time: 2m 51s Verified: yes Solution Problem Understanding We are given an array of integers representing the skill levels of students. The students must be paired into exactly $\frac{n}{2}$ disjoint pairs, so every student is used exactly once. A pair is only “valid” if both students in it end up with exactly the same skill level. Since skills can only...

CF 1091E - New Year and the Acquaintance Estimation

CF 1091E - New Year and the Acquaintance Estimation Rating: 2400 Tags: binary search, data structures, graphs, greedy, implementation, math, sortings Solve time: 4m 22s Verified: no Solution Problem Understanding We are given a simple undirected graph on $n+1$ vertices, but one vertex is missing from the data. Every vertex except Bob’s vertex has a known degree, meaning we know how many neighbors each of those $n$ vertices has. The...

CF 920C - Swap Adjacent Elements

CF 920C - Swap Adjacent Elements Rating: 1400 Tags: dfs and similar, greedy, math, sortings, two pointers Solve time: 2m 30s Verified: yes Solution Problem Understanding We are given a permutation of size n, meaning every integer from 1 to n appears exactly once. Alongside this array is a string that describes which adjacent positions are “connected” by an allowed swap. If the i-th character is 1, we are allowed...

CF 915E - Physical Education Lessons

CF 915E - Physical Education Lessons Rating: 2300 Tags: data structures, implementation, sortings Solve time: 7m 46s Verified: no Solution Problem Understanding We are managing a line of days from 1 to n, where each day can be either working or non-working. Initially every day is working. Then a sequence of updates arrives, and after each update we must report how many working days currently exist. Each update affects a...

CF 913D - Too Easy Problems

CF 913D - Too Easy Problems Rating: 1800 Tags: binary search, brute force, data structures, greedy, sortings Solve time: 6m 50s Verified: no Solution Problem Understanding We are given a set of exam problems, each with a solving time and a “strictness limit” that controls whether it contributes to our score. We can pick any subset of problems to solve as long as the total time does not exceed the...

CF 912C - Perun, Ult!

CF 912C - Perun, Ult! Rating: 2500 Tags: brute force, greedy, sortings Solve time: 5m 1s Verified: yes Solution Problem Understanding We are asked to choose a single moment in time to cast a global ability that deals fixed damage to all enemies, with the goal of maximizing the gold gained from kills. Each enemy has initial health, regenerates health over time at a constant rate, and can have discrete...

CF 909A - Generate Login

CF 909A - Generate Login Rating: 1000 Tags: brute force, greedy, sortings Solve time: 11m 29s Verified: yes Solution Problem Understanding We are asked to construct a login from a user's first and last names by concatenating a non-empty prefix of the first name with a non-empty prefix of the last name. The key requirement is that among all possible concatenations, we must select the one that is alphabetically smallest....

Codeforces Round 572 (Div. 2)

Codeforces Round 572 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 800-1400 | Time: 9m 36s Problem Name Rating Tags Solve Time Verified A Keanu Reeves 800 strings 2m 54s ✓ B Number Circle 1100 greedy, math, sortings 1m 33s ✓ C Candies! 1400 data-structures, dp, implementation 5m 9s ✓

Educational Codeforces Round 37 (Rated for Div. 2)

Educational Codeforces Round 37 (Rated for Div. 2) Div. 2 | 7 problems | 6/7 verified | Difficulty 1000-2400 | 30m 58s # Problem Rating Tags Accepted Time ✓ A Water The Garden 1000 implementation 8,195 2m 8s ✓ B Tea Queue 1200 implementation 8,101 5m 21s C Swap Adjacent Elements 1400 dfs-and-similar, greedy, math 9,970 2m 30s ✓ D Tanks 2400 dp, greedy, implementation 809 10m 3s ✓ E...

Helvetic Coding Contest 2019 online mirror (teams allowed, unrated)

Helvetic Coding Contest 2019 online mirror (teams allowed, unrated) Type: Special | Problems: 14 | Verified: 11/14 | Rating range: 1200-3200 | Time: 56m 25s Problem Name Rating Tags Solve Time Verified A1 Heidi Learns Hashing (Easy) 1200 brute-force, math, number-theory 3m 46s ✓ A2 Heidi Learns Hashing (Medium) 2100 brute-force, number-theory 1m 26s ✓ A3 Heidi Learns Hashing (Hard) 3100 fft, math, number-theory 7m 45s ✓ B1 The Doctor...

Codeforces Round 570 (Div. 3)

Codeforces Round 570 (Div. 3) Type: Div. 3 | Problems: 8 | Verified: 7/8 | Rating range: 800-2100 | Time: 36m 3s Problem Name Rating Tags Solve Time Verified A Nearest Interesting Number 800 implementation 1m 17s ✓ B Equalize Prices 900 math 9m 40s ✗ C Computer Game 1400 binary-search, math 7m 29s ✓ D Candy Box (easy version) 1400 greedy, sortings 2m 22s ✓ E Subsequences (easy version)...

Codeforces Round 560 (Div. 3)

Codeforces Round 560 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 5/7 | Rating range: 1000-2000 | Time: 26m 28s Problem Name Rating Tags Solve Time Verified A Remainder 1100 implementation, math 1m 29s ✓ B Polycarp Training 1000 data-structures, greedy, sortings 1m 25s ✗ C Good String 1300 greedy 4m 3s ✓ D Almost All Divisors 1600 math, number-theory 6m 29s ✓ E Two Arrays and Sum...

Codeforces Round 531 (Div. 3)

Codeforces Round 531 (Div. 3) Type: Div. 3 | Problems: 6 | Verified: 3/6 | Rating range: 800-2000 | Time: 26m 9s Problem Name Rating Tags Solve Time Verified A Integer Sequence Dividing 800 math 1m 12s ✓ B Array K-Coloring 1400 greedy, sortings 7m 32s ✗ C Doors Breaking and Repairing 1200 games 5m 1s ✓ D Balanced Ternary String 1500 greedy, strings 5m 57s ✗ E Monotonic Renumeration...

CF 1106C - Lunar New Year and Number Division

CF 1106C - Lunar New Year and Number Division Rating: 900 Tags: greedy, implementation, math, sortings Solve time: 1m 15s Verified: yes Solution Problem Understanding We are given an even-length list of positive integers, and we must partition these numbers into groups. Each group must contain at least two elements, and every number must belong to exactly one group. For each group, we compute the sum of its elements, square...

Educational Codeforces Round 59 (Rated for Div. 2)

Educational Codeforces Round 59 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 4/7 | Rating range: 900-2600 | Time: 14m 22s Problem Name Rating Tags Solve Time Verified A Digits Sequence Dividing 900 greedy, strings 1m 36s ✓ B Digital root 1000 math, number-theory 1m 10s ✓ C Brutality 1300 greedy, sortings, two-pointers 5m 27s ✗ D Compression 1800 dp, implementation, math 1m 25s ✓ E...

CF 1107C - Brutality

CF 1107C - Brutality Rating: 1300 Tags: greedy, sortings, two pointers Solve time: 5m 27s Verified: no Solution Problem Understanding We are given a fixed sequence of hits, where each hit has a damage value and is associated with a specific button (a lowercase letter). We are allowed to delete any hits from the sequence while keeping the remaining ones in their original order. The total damage is the sum...

CF 1107F - Vasya and Endless Credits

CF 1107F - Vasya and Endless Credits Rating: 2600 Tags: dp, flows, graph matchings, graphs, sortings Solve time: 1m 57s Verified: no Solution Problem Understanding Vasya starts with zero burles and wants to buy a car. The bank offers n credit deals, each giving him an initial sum a_i immediately and requiring monthly payments of b_i for k_i months. Vasya can take at most one credit per month, but multiple...

Codeforces Global Round 1

Codeforces Global Round 1 Type: Global | Problems: 8 | Verified: 5/8 | Rating range: 900-3500 | Time: 15m 41s Problem Name Rating Tags Solve Time Verified A Parity 900 math 5m 9s ✗ B Tape 1400 greedy, sortings 1m 32s ✓ C Meaningless Operations 1500 constructive-algorithms, math, number-theory 1m 33s ✓ D Jongmah 2200 dp 1m 38s ✗ E Magic Stones 2200 constructive-algorithms, math, sortings 1m 10s ✓ F...

CF 1110E - Magic Stones

CF 1110E - Magic Stones Rating: 2200 Tags: constructive algorithms, math, sortings Solve time: 1m 10s Verified: yes Solution Problem Understanding We are given an array of integers representing charges on a line of stones. A single operation picks any interior position and replaces its value using its two neighbors: the new value becomes the sum of the left and right neighbors minus its old value. The endpoints are never...

CF 1110B - Tape

CF 1110B - Tape Rating: 1400 Tags: greedy, sortings Solve time: 1m 32s Verified: yes Solution Problem Understanding We are given a sorted list of positions on a long line segment where damage has occurred. Each damaged position must be covered by tape, but the tape does not need to avoid healthy positions, it can freely cover anything in between. The tape can be cut into at most k continuous...

Codeforces Round 538 (Div. 2)

Codeforces Round 538 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2400 | Time: 12m 30s Problem Name Rating Tags Solve Time Verified A Got Any Grapes? 800 brute-force, greedy, implementation 5m 24s ✗ B Yet Another Array Partitioning Task 1500 constructive-algorithms, greedy, sortings 1m 52s ✓ C Trailing Loves (or L'oeufs?) 1700 brute-force, implementation, math 1m 4s ✓ D Flood Fill 1900 dp...

CF 1114B - Yet Another Array Partitioning Task

CF 1114B - Yet Another Array Partitioning Task Rating: 1500 Tags: constructive algorithms, greedy, sortings Solve time: 1m 52s Verified: yes Solution Problem Understanding We are given a sequence of integers a of length n , and two parameters: m , the number of largest elements we consider when computing the "beauty" of a subarray, and k , the number of contiguous subarrays we must partition a into. A subarray’s...

Educational Codeforces Round 60 (Rated for Div. 2)

Educational Codeforces Round 60 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 3/7 | Rating range: 1000-2500 | Time: 14m 48s Problem Name Rating Tags Solve Time Verified A Best Subsegment 1100 implementation, math 5m 30s ✗ B Emotes 1000 greedy, math, sortings 1m 28s ✓ C Magic Ship 1900 binary-search 1m 19s ✓ D Magic Gems 2100 dp, math, matrices 1m 24s ✗ E Decypher...

CF 1117B - Emotes

CF 1117B - Emotes Rating: 1000 Tags: greedy, math, sortings Solve time: 1m 28s Verified: yes Solution Problem Understanding We are given a set of emotes, each with a positive happiness value. We are allowed to use emotes a fixed number of times, but no single emote can be repeated more than a given number of times consecutively. The task is to maximize the total happiness delivered to the opponent...

Codeforces Global Round 2

Codeforces Global Round 2 Type: Global | Problems: 8 | Verified: 6/8 | Rating range: 1100-3400 | Time: 10m 34s Problem Name Rating Tags Solve Time Verified A Ilya and a Colorful Walk 1100 greedy, implementation 1m 5s ✓ B Alyona and a Narrow Fridge 1300 binary-search, flows, greedy 1m 54s ✓ C Ramesses and Corner Inversion 1500 constructive-algorithms, greedy, implementation 1m 4s ✓ D Frets On Fire 1800 binary-search,...

CF 1119B - Alyona and a Narrow Fridge

CF 1119B - Alyona and a Narrow Fridge Rating: 1300 Tags: binary search, flows, greedy, sortings Solve time: 1m 54s Verified: yes Solution Problem Understanding The fridge has height h and exactly two columns. Shelves can be inserted at any heights, which means we are free to divide the fridge into horizontal compartments of arbitrary heights. Each bottle occupies one column and has height a[i] . The task is not...

Codeforces Round 543 (Div. 2, based on Technocup 2019 Final Round)

Codeforces Round 543 (Div. 2, based on Technocup 2019 Final Round) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 1100-1600 | Time: 4m 20s Problem Name Rating Tags Solve Time Verified A Technogoblet of Fire 1100 implementation, sortings 1m 6s ✓ B Mike and Children 1200 brute-force, implementation 1m 12s ✓ C System Testing 1600 implementation 2m 2s ✓

CF 1121A - Technogoblet of Fire

CF 1121A - Technogoblet of Fire Rating: 1100 Tags: implementation, sortings Solve time: 1m 6s Verified: yes Solution Problem Understanding We are given a set of students, each belonging to a school, and each with a power rating. The tournament rule is simple: only the strongest student from each school gets selected. Arkady wants to ensure that a chosen set of k students are selected. Some of these students may...

CF 1129C - Morse Code

CF 1129C - Morse Code Rating: 2400 Tags: binary search, data structures, dp, hashing, sortings, string suffix structures, strings Solve time: 1m 24s Verified: no Solution Problem Understanding We are asked to track sequences of English letters encoded in Morse code as we build a string incrementally, one character at a time. The string S starts empty and grows by adding either a dot ( 0 ) or a dash...

Codeforces Round 541 (Div. 2)

Codeforces Round 541 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 4/7 | Rating range: 800-2700 | Time: 10m 40s Problem Name Rating Tags Solve Time Verified A Sea Battle 800 math 2m 2s ✓ B Draw! 1400 greedy, implementation 1m 16s ✓ C Birthday 1200 binary-search, greedy, sortings 1m 28s ✓ D Gourmet choice 2000 dfs-and-similar, dp, dsu 1m 28s ✗ E String Multiplication 2300 dp, greedy,...

CF 1131C - Birthday

CF 1131C - Birthday Rating: 1200 Tags: binary search, greedy, sortings Solve time: 1m 28s Verified: yes Solution Problem Understanding We are asked to arrange a group of children in a circle such that the maximum height difference between any two adjacent children is as small as possible. The input provides the number of children n and an array of their heights. The output is a permutation of these heights...

Educational Codeforces Round 61 (Rated for Div. 2)

Educational Codeforces Round 61 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 6/7 | Rating range: 900-2400 | Time: 10m 4s Problem Name Rating Tags Solve Time Verified A Regular Bracket Sequence 1100 greedy, implementation 1m 10s ✓ B Discounts 900 greedy, sortings 1m 13s ✓ C Painting the Fence 1700 brute-force 2m 2s ✓ D Stressful Training 2300 binary-search, greedy 1m 23s ✗ E Knapsack...

CF 1132B - Discounts

CF 1132B - Discounts Rating: 900 Tags: greedy, sortings Solve time: 1m 13s Verified: yes Solution Problem Understanding We have a set of chocolate bars, each with its own price. The shopper wants all the bars but has a selection of discount coupons. Each coupon allows buying a fixed number of bars, but within that selection, the cheapest bar is free. The task is to determine, for each coupon, the...

Codeforces Round 544 (Div. 3)

Codeforces Round 544 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 5/7 | Rating range: 1000-1900 | Time: 9m 17s Problem Name Rating Tags Solve Time Verified A Middle of the Contest 1000 implementation 1m 7s ✓ B Preparation for International Women's Day 1200 math, number-theory 1m 14s ✓ C Balanced Team 1200 sortings, two-pointers 1m 9s ✓ D Zero Quantity Maximization 1500 hashing, math, number-theory 1m 13s...

CF 1133E - K Balanced Teams

CF 1133E - K Balanced Teams Rating: 1800 Tags: dp, sortings, two pointers Solve time: 1m 5s Verified: yes Solution Problem Understanding We have a list of students, each with a programming skill level. The task is to divide these students into at most k teams so that the total number of students included is maximized. Each team must be "balanced," meaning that no two students in the same team...

CF 1133C - Balanced Team

CF 1133C - Balanced Team Rating: 1200 Tags: sortings, two pointers Solve time: 1m 9s Verified: yes Solution Problem Understanding We have a list of students, each with a programming skill score. The task is to form the largest possible team such that the difference between the highest-skilled and lowest-skilled members does not exceed 5. In other words, for any team of size $k$, if the skills are $s_1, s_2,...

Codeforces Round 546 (Div. 2)

Codeforces Round 546 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2200 | Time: 8m 33s Problem Name Rating Tags Solve Time Verified A Nastya Is Reading a Book 800 implementation 1m 18s ✓ B Nastya Is Playing Computer Games 1000 constructive-algorithms, math 2m ✓ C Nastya Is Transposing Matrices 1500 constructive-algorithms, sortings 1m 49s ✓ D Nastya Is Buying Lunch 1800 greedy 1m...

CF 1136C - Nastya Is Transposing Matrices

CF 1136C - Nastya Is Transposing Matrices Rating: 1500 Tags: constructive algorithms, sortings Solve time: 1m 49s Verified: yes Solution Problem Understanding We are given two matrices of the same size, A and B . The allowed operation is surprisingly powerful: we may choose any square submatrix inside A and transpose it. Transposition swaps positions relative to the square's main diagonal. We may perform this operation any number of times...

Codeforces Round 545 (Div. 1)

Codeforces Round 545 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 3/6 | Rating range: 1600-3400 | Time: 9m 34s Problem Name Rating Tags Solve Time Verified A Skyscrapers 1600 implementation, sortings 1m 41s ✗ B Camp Schedule 1600 greedy, hashing, strings 1m 51s ✓ C Museums Tour 2500 dp, graphs, implementation 1m 25s ✓ D Cooperative Game 2400 constructive-algorithms, interactive, number-theory 1m 47s ✗ E Train Car...

CF 1137A - Skyscrapers

CF 1137A - Skyscrapers Rating: 1600 Tags: implementation, sortings Solve time: 1m 41s Verified: no Solution Problem Understanding We are given a city laid out as a grid of size $n \times m$, where each cell represents an intersection containing a skyscraper of a certain height. For each intersection at row $i$ and column $j$, we focus on two lines of skyscrapers: the full $i$-th row (Eastern street) and the...

Educational Codeforces Round 62 (Rated for Div. 2)

Educational Codeforces Round 62 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 6/7 | Rating range: 1000-2700 | Time: 10m 24s Problem Name Rating Tags Solve Time Verified A Detective Book 1000 implementation 1m 21s ✓ B Good String 1200 implementation, strings 1m 45s ✓ C Playlist 1600 brute-force, data-structures, sortings 1m 29s ✓ D Minimum Triangulation 1200 dp, greedy, math 1m 21s ✓ E Palindrome-less...

CF 1140C - Playlist

CF 1140C - Playlist Rating: 1600 Tags: brute force, data structures, sortings Solve time: 1m 29s Verified: yes Solution Problem Understanding Each song has two attributes: its length t and its beauty b . If we choose some subset of songs, its score is $$(\text{sum of lengths}) \times (\text{minimum beauty})$$ We may choose at most k songs, and we want the maximum possible score. The interesting part is that the...

Codeforces Round 550 (Div. 3)

Codeforces Round 550 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 3/7 | Rating range: 800-2400 | Time: 12m 3s Problem Name Rating Tags Solve Time Verified A Diverse Strings 800 implementation, strings 1m 18s ✓ B Parity Alternated Deletions 900 greedy, implementation, sortings 1m 18s ✓ C Two Shuffled Sequences 1000 constructive-algorithms, sortings 1m 48s ✗ D Equalize Them All 1400 constructive-algorithms, greedy 3m 16s ✗ E...

CF 1144C - Two Shuffled Sequences

CF 1144C - Two Shuffled Sequences Rating: 1000 Tags: constructive algorithms, sortings Solve time: 1m 48s Verified: no Solution Problem Understanding We are given a multiset of integers that was created by taking two sequences, one strictly increasing and one strictly decreasing, merging all their elements together, and then shuffling the result. The original order inside the merged array is lost. We only know the values that appeared. Our task...

CF 1144B - Parity Alternated Deletions

CF 1144B - Parity Alternated Deletions Rating: 900 Tags: greedy, implementation, sortings Solve time: 1m 18s Verified: yes Solution Problem Understanding We are given a sequence of integers, and we are allowed to remove elements one by one under a parity constraint that depends on the previous deletion. The first removed element can be anything. After that, every removal must alternate parity relative to the last removed element: if we...

Codeforces Global Round 3

Codeforces Global Round 3 Type: Global | Problems: 8 | Verified: 2/8 | Rating range: 800-3500 | Time: 12m 46s Problem Name Rating Tags Solve Time Verified A Another One Bites The Dust 800 greedy 1m 38s ✓ B Born This Way 1600 binary-search, brute-force, two-pointers 32s ✗ C Crazy Diamond 1700 constructive-algorithms, sortings 3m 19s ✓ D Dirty Deeds Done Dirt Cheap 1800 greedy, sortings 36s ✗ E Earth...

CF 1148C - Crazy Diamond

CF 1148C - Crazy Diamond Rating: 1700 Tags: constructive algorithms, sortings Solve time: 3m 19s Verified: yes Solution Problem Understanding We are given a permutation of the numbers from 1 to $n$, where $n$ is guaranteed to be even. A permutation means each number appears exactly once in the array. The task is to sort this permutation in ascending order. However, there is a constraint on the allowed swaps: you...

CF 1148E - Earth Wind and Fire

CF 1148E - Earth Wind and Fire Rating: 2300 Tags: constructive algorithms, greedy, math, sortings, two pointers Solve time: 1m 43s Verified: no Solution Problem Understanding We are given two multisets of integer positions on a number line. One multiset describes where stones start, the other describes where we want them to end. Stones are indistinguishable except for their current positions, and we are allowed to perform operations that simultaneously...

CF 1148D - Dirty Deeds Done Dirt Cheap

CF 1148D - Dirty Deeds Done Dirt Cheap Rating: 1800 Tags: greedy, sortings Solve time: 36s Verified: no Solution Problem Understanding We are given a collection of $n$ disjoint pairs of integers. Every integer from $1$ to $2n$ appears exactly once across all pairs, so each number belongs to exactly one pair and there is no overlap. We are allowed to pick some of these pairs and arrange the chosen...

CF 1151D - Stas and the Queue at the Buffet

CF 1151D - Stas and the Queue at the Buffet Rating: 1600 Tags: greedy, math, sortings Solve time: 3m 3s Verified: yes Solution Problem Understanding We have a queue of students, each with two personal characteristics: $a_i$, which measures how much they dislike people in front of them, and $b_i$, which measures how much they dislike people behind them. The dissatisfaction of a student depends linearly on their position: if...

CF 1154E - Two Teams

CF 1154E - Two Teams Rating: 1800 Tags: data structures, implementation, sortings Solve time: 1m 58s Verified: yes Solution Problem Understanding We are given a row of n students, each with a distinct programming skill ranging from 1 to n . Two coaches take turns picking students to form their teams. On a coach's turn, they select the student with the highest skill remaining in the row. Then, in addition...

Codeforces Round 552 (Div. 3)

Codeforces Round 552 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 5/7 | Rating range: 800-2200 | Time: 9m 33s Problem Name Rating Tags Solve Time Verified A Restoring Three Numbers 800 math 1m 31s ✗ B Make Them Equal 1200 math 43s ✗ C Gourmet Cat 1400 implementation, math 1m 30s ✓ D Walking Robot 1500 greedy 1m 15s ✓ E Two Teams 1800 data-structures, implementation, sortings...

CF 1154F - Shovels Shop

CF 1154F - Shovels Shop Rating: 2100 Tags: dp, greedy, sortings Solve time: 1m 23s Verified: yes Solution Problem Understanding We have a shop with n shovels, each with a specific price. Misha wants to buy exactly k shovels, possibly in multiple purchases. The twist is that the shop offers special deals: if you buy exactly x_j shovels in a single purchase, the y_j cheapest among those shovels are free....

Educational Codeforces Round 63 (Rated for Div. 2)

Educational Codeforces Round 63 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 1000-2800 | Time: 11m 57s Problem Name Rating Tags Solve Time Verified A Reverse a Substring 1000 implementation, sortings, strings 3m 29s ✗ B Game with Telephone Numbers 1200 games, greedy, implementation 1m 27s ✓ C Alarm Clocks Everywhere 1300 math, number-theory 1m 31s ✓ D Beautiful Array 1900 brute-force,...

CF 1155A - Reverse a Substring

CF 1155A - Reverse a Substring Rating: 1000 Tags: implementation, sortings, strings Solve time: 3m 29s Verified: no Solution Problem Understanding We are given a single string made of lowercase English letters. We are allowed to choose one contiguous segment inside this string and reverse that segment exactly once. After performing this single reversal, we obtain a new string. The task is to determine whether there exists any such reversal...

Educational Codeforces Round 64 (Rated for Div. 2)

Educational Codeforces Round 64 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 4/7 | Rating range: 1400-2700 | Time: 10m 55s Problem Name Rating Tags Solve Time Verified A Inscribed Figures 1400 geometry 1m 31s ✓ B Ugly Pairs 1800 dfs-and-similar, greedy, implementation 1m 46s ✗ C Match Points 2000 binary-search, greedy, sortings 1m 18s ✓ D 0-1-Tree 2200 dfs-and-similar, divide-and-conquer, dp 1m 42s ✗ E...

CF 1156B - Ugly Pairs

CF 1156B - Ugly Pairs Rating: 1800 Tags: dfs and similar, greedy, implementation, sortings, strings Solve time: 1m 46s Verified: no Solution Problem Understanding We are given a short string of lowercase letters and we are allowed to reorder its characters arbitrarily. The goal is to produce an arrangement where no two adjacent characters differ by exactly one position in the alphabet. For example, placing ‘c’ next to ‘d’ or...

CF 1156C - Match Points

CF 1156C - Match Points Rating: 2000 Tags: binary search, greedy, sortings, ternary search, two pointers Solve time: 1m 18s Verified: yes Solution Problem Understanding We are given a collection of points placed on a number line, and the goal is to form as many disjoint pairs as possible. A pair is valid only if the two chosen points are far enough apart, meaning the absolute difference between their coordinates...

Codeforces Round 559 (Div. 1)

Codeforces Round 559 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 1/6 | Rating range: 1500-3500 | Time: 10m 32s Problem Name Rating Tags Solve Time Verified A The Party and Sweets 1500 binary-search, constructive-algorithms, greedy 2m 36s ✗ B The minimal unique substring 2200 constructive-algorithms, math, strings 1m 20s ✓ C Permutation recovery 2100 constructive-algorithms, data-structures, dfs-and-similar 1m 37s ✗ D Winding polygonal line 2600 constructive-algorithms, geometry,...

CF 1158C - Permutation recovery

CF 1158C - Permutation recovery Rating: 2100 Tags: constructive algorithms, data structures, dfs and similar, graphs, greedy, math, sortings Solve time: 1m 37s Verified: no Solution Problem Understanding We are asked to reconstruct a permutation of numbers from 1 to n given a partially known array called next . Each element next[i] represents the smallest index j greater than i such that p[j] > p[i] . If no such j...

CF 1158A - The Party and Sweets

CF 1158A - The Party and Sweets Rating: 1500 Tags: binary search, constructive algorithms, greedy, implementation, math, sortings, two pointers Solve time: 2m 36s Verified: no Solution Problem Understanding We have a party with $n$ boys and $m$ girls. Each boy gives some number of sweets to every girl, forming an $n \times m$ matrix of integers. For each boy, the minimum number of sweets he gives to any girl...

CF 1165E - Two Arrays and Sum of Functions

CF 1165E - Two Arrays and Sum of Functions Rating: 1600 Tags: greedy, math, sortings Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given two arrays of equal length, where one array is fixed and the other can be permuted arbitrarily. After choosing an ordering of the second array, we assign its values position by position against the first array. From this paired array we compute, for...

CF 1166C - A Tale of Two Lands

CF 1166C - A Tale of Two Lands Rating: 1500 Tags: binary search, sortings, two pointers Solve time: 1m 27s Verified: yes Solution Problem Understanding We are given a set of integers representing potential values for two historical markers, $x$ and $y$. For each candidate pair of distinct integers $(x, y)$, we compute two intervals on the number line. The first interval, called Arrayland, is determined by the absolute values...

CF 1174B - Ehab Is an Odd Person

CF 1174B - Ehab Is an Odd Person Rating: 1200 Tags: sortings Solve time: 1m 33s Verified: yes Solution Problem Understanding We are given a sequence of numbers, and we are allowed to reorder it, but with a restriction on how swaps work. A swap is only legal if we pick two positions whose values have opposite parity, meaning one is odd and the other is even. If both are...

CF 1176F - Destroy it!

CF 1176F - Destroy it! Rating: 2100 Tags: dp, implementation, sortings Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given a sequence of turns in a card game. On each turn, the player receives a set of cards, each with a cost and a damage value. The player can play any subset of cards in that turn as long as the total cost does not exceed 3....

CF 1181E1 - A Story of One Country (Easy)

CF 1181E1 - A Story of One Country (Easy) Rating: 2500 Tags: brute force, divide and conquer, sortings Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given n castles on a 2D plane, each represented by an axis-aligned rectangle with integer coordinates. Each castle originally belonged to a country whose territory was also a rectangle. The story claims that countries could merge if their union formed a...

CF 1184B2 - The Doctor Meets Vader (Medium)

CF 1184B2 - The Doctor Meets Vader (Medium) Rating: 2200 Tags: flows, graph matchings, graphs, shortest paths, sortings Solve time: 2m 6s Verified: yes Solution Problem Understanding The galaxy is a small graph of planets connected by wormholes, where distance between planets is measured as the minimum number of edges in this graph. On top of this infrastructure, there are two kinds of actors: empire ships and rebel bases. Each...

CF 1185C1 - Exam in BerSU (easy version)

CF 1185C1 - Exam in BerSU (easy version) Rating: 1200 Tags: greedy, sortings Solve time: 1m 40s Verified: yes Solution Problem Understanding We are given a sequence of students, each associated with a fixed amount of time they would spend if they successfully pass their exam. Students arrive in order, and if a student is allowed to pass, they consume time equal to their own value; otherwise, they immediately fail...

CF 1189B - Number Circle

CF 1189B - Number Circle Rating: 1100 Tags: greedy, math, sortings Solve time: 1m 33s Verified: yes Solution Problem Understanding We are given a multiset of numbers and asked whether we can place all of them around a circle so that every element is strictly smaller than the sum of its two adjacent elements. The adjacency is circular, so the first and last elements are also neighbors. The condition is...

CF 1197C - Array Splitting

CF 1197C - Array Splitting Rating: 1400 Tags: greedy, sortings Solve time: 1m 27s Verified: yes Solution Problem Understanding We are given a non-decreasing array and asked to split it into exactly $k$ contiguous parts. Each part contributes a cost equal to the difference between its largest and smallest element, and since the array is sorted, this is simply the difference between its last and first element in that segment....

CF 1203E - Boxers

CF 1203E - Boxers Rating: 1500 Tags: greedy, sortings Solve time: 1m 17s Verified: yes Solution Problem Understanding We are given a set of boxers, each with a positive integer weight. Each boxer can adjust their weight by at most 1, either up or down, but the weight must remain strictly positive. Our goal is to form the largest possible team in which no two boxers share the same weight...

CF 1209E1 - Rotate Columns (easy version)

CF 1209E1 - Rotate Columns (easy version) Rating: 2000 Tags: bitmasks, brute force, dp, greedy, sortings Solve time: 1m 58s Verified: yes Solution Problem Understanding We are given a matrix with n rows and m columns, where each entry is a positive integer. We can pick any column and rotate it cyclically any number of times. After performing such rotations, we consider each row and take the maximum value in...

CF 1213D2 - Equalizing by Division (hard version)

CF 1213D2 - Equalizing by Division (hard version) Rating: 1600 Tags: brute force, math, sortings Solve time: 1m 46s Verified: yes Solution Problem Understanding We are given an array of integers, and we can repeatedly pick any number and divide it by two, rounding down. The goal is to find the minimum number of such operations required to make at least $k$ numbers in the array equal. Each operation decreases...

CF 1214F - Employment

CF 1214F - Employment Rating: 2700 Tags: greedy, sortings Solve time: 2m 40s Verified: yes Solution Problem Understanding We have two multisets of points on a circle of length m . The first set contains the office locations. Office i is located in city a[i] . The second set contains the candidates. Candidate j lives in city b[j] . Every office must receive exactly one candidate and every candidate must...

Educational Codeforces Round 76 (Rated for Div. 2)

Educational Codeforces Round 76 (Rated for Div. 2) Div. 2 | 7 problems | 5/7 verified | Difficulty 800-2600 | 33m 32s # Problem Rating Tags Accepted Time ✓ A Two Rival Students 800 greedy, math 21,661 2m 1s ✓ B Magic Stick 1000 math 22,520 11m 28s C Dominated Subarray 1200 greedy, implementation, sortings 17,143 4m 19s ✓ D Yet Another Monster Killing Problem 1700 binary-search, data-structures, dp 8,172...

CF 1216B - Shooting

CF 1216B - Shooting Rating: 900 Tags: greedy, implementation, sortings Solve time: 2m 12s Verified: yes Solution Problem Understanding We are given a line of cans, each with a durability value. Vasya has to shoot all cans exactly once, but the number of shots required to knock down a can depends on how many cans have already been knocked down. Specifically, if a can has durability $a_i$ and Vasya has...

CF 1253C - Sweets Eating

CF 1253C - Sweets Eating Rating: 1500 Tags: dp, greedy, math, sortings Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given a list of sweets, each with a positive integer value representing its sweetness level. Yui wants to eat exactly $k$ sweets for each $k$ from 1 to $n$. However, she cannot eat more than $m$ sweets in a single day. Time is divided into days starting...

Educational Codeforces Round 74 (Rated for Div. 2)

Educational Codeforces Round 74 (Rated for Div. 2) Div. 2 | 7 problems | 3/7 verified | Difficulty 900-2700 | 30m 18s # Problem Rating Tags Accepted Time ✓ A Prime Subtraction 900 math, number-theory 28,046 1m 23s ✓ B Kill `Em All 1300 greedy, sortings 14,874 2m 33s C Standard Free2play 1600 dp, greedy, math 7,851 6m 2s D AB-string 1900 binary-search, combinatorics, dp 6,442 6m 17s E Keyboard...

Codeforces Round 609 (Div. 2)

Codeforces Round 609 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1500-1500 | Time: 1m 58s Problem Name Rating Tags Solve Time Verified B Modulo Equality 1500 brute-force, sortings 1m 58s ✓

CF 1269B - Modulo Equality

CF 1269B - Modulo Equality Rating: 1500 Tags: brute force, sortings Solve time: 1m 58s Verified: yes Solution Problem Understanding We have two arrays of equal length. We may choose a single non-negative value x , add it to every element of the first array, and take all results modulo m . After this transformation, the order of elements does not matter. We are allowed to rearrange the transformed array...

CF 1286A - Garland

CF 1286A - Garland Rating: 1800 Tags: dp, greedy, sortings Solve time: 2m 42s Verified: yes Solution Problem Understanding We are given a row of n bulbs, each numbered from 1 to n . Some bulbs are missing, indicated by zeros in the input array. Our goal is to fill in the missing bulbs using the numbers that are not already present, and to place them in a sequence that...

CF 1296E1 - String Coloring (easy version)

CF 1296E1 - String Coloring (easy version) Rating: 1800 Tags: constructive algorithms, dp, graphs, greedy, sortings Solve time: 2m 3s Verified: yes Solution Problem Understanding We have a string of lowercase letters. Every position must be assigned one of two colors, 0 or 1. After choosing the colors, we are allowed to swap neighboring characters only when their colors are different. We may perform such swaps as many times as...

CF 1297B - Cartoons

CF 1297B - Cartoons Rating: - Tags: *special, implementation, sortings Solve time: 3m 5s Verified: no Solution There is not enough information to diagnose the bug or provide a corrected solution. The sample 3 3 tab one bat with expected output 6 tabbat appears to belong to a string construction problem, but you have not provided: the problem statement, the original Python solution, or even the name of the problem....

Codeforces Round 650 (Div. 3)

Codeforces Round 650 (Div. 3) Div. 3 | 7 problems | 4/7 verified | Difficulty 800-2400 | 23m 6s # Problem Rating Tags Accepted Time ✓ A Short Substrings 800 implementation, strings 67,694 1m 59s ✓ B Even Array 800 greedy, math 63,923 3m 58s ✓ C Social Distance 1300 constructive-algorithms, greedy, math 25,103 3m 5s D Task On The Board 1800 constructive-algorithms, greedy, implementation 8,788 6m 59s E Necklace...

Codeforces Round 644 (Div. 3)

Codeforces Round 644 (Div. 3) Div. 3 | 8 problems | 6/8 verified | Difficulty 800-2100 | 30m 13s # Problem Rating Tags Accepted Time ✓ A Minimal Square 800 greedy, math 57,075 1m 35s ✓ B B 800 greedy, sortings 53,706 3m 38s ✓ C Similar Pairs 1100 constructive-algorithms, graph-matchings, greedy 36,772 4m 42s ✓ D D 1300 math, number theory 42,975 5m 7s ✓ E Polygon 1300 dp,...

Kotlin Heroes: Episode 4

Kotlin Heroes: Episode 4 Kotlin | 9 problems | 4/9 verified | Difficulty 1000-2900 | 40m 15s # Problem Rating Tags Accepted Time ✓ A Color Revolution 1000 *special, math 2,202 11m 53s ✓ B Boot Camp 1400 *special, greedy 1,252 3m 10s C Spring Cleaning 1600 *special, greedy, sortings 677 5m 16s D Constructing the Dungeon 1600 *special, graphs, greedy 544 2m 56s ✓ E Magic Tricks 1700 *special,...

Ozon Tech Challenge 2020 (Div.1 + Div.2, Rated, T-shirts + prizes!)

Ozon Tech Challenge 2020 (Div.1 + Div.2, Rated, T-shirts + prizes!) Special | 8 problems | 3/8 verified | Difficulty 800-3500 | 38m 8s # Problem Rating Tags Accepted Time ✓ A Kuroni and the Gifts 800 brute-force, constructive-algorithms, greedy 14,644 1m 48s B Kuroni and Simple Strings 1200 constructive-algorithms, greedy, strings 12,397 16m 28s C C 1600 brute force, combinatorics, math 18,774 1m 52s ✓ D Kuroni and the...

CF 1304C - Air Conditioner

CF 1304C - Air Conditioner Rating: 1500 Tags: dp, greedy, implementation, sortings, two pointers Solve time: 1m 33s Verified: no Solution Yes, the inequality $\nu(n) \le 2^{l(n) - \lambda(n)}$ holds for all positive integers $n$. Consider an addition chain of minimal length $l(n)$ and let $\lambda(n)$ be the length of a shortest chain consisting only of doubling steps. Each nondoubling step can at most double the number of ones in...

Educational Codeforces Round 77 (Rated for Div. 2)

Educational Codeforces Round 77 (Rated for Div. 2) Div. 2 | 5 problems | 4/5 verified | Difficulty 1000-2700 | 19m 39s # Problem Rating Tags Accepted Time ✓ A Heating 1000 math 15,814 2m 22s ✓ C Infinite Fence 1700 greedy, math, number-theory 8,782 2m 47s D A Game with Traps 1900 binary-search, dp, greedy 4,189 10m 47s ✓ E Tournament 2400 brute-force, dp, greedy 1,890 1m 15s ✓...

Codeforces Round 598 (Div. 3)

Codeforces Round 598 (Div. 3) Div. 3 | 3 problems | 1/3 verified | Difficulty 1000-2000 | 5m 2s # Problem Rating Tags Accepted Time ✓ A Payment Without Change 1000 math 32,430 1m 50s ✓ B Minimize the Permutation 1400 greedy 13,682 1m 47s F Equalizing Two Strings 2000 constructive-algorithms, sortings, strings 3,621 1m 25s

Codeforces Round 600 (Div. 2)

Codeforces Round 600 (Div. 2) Div. 2 | 5 problems | 2/5 verified | Difficulty 1400-2500 | 9m 50s # Problem Rating Tags Accepted Time ✓ B Silly Mistake 1400 greedy, implementation 11,704 2m 45s C Sweets Eating 1500 dp, greedy, math 15,301 1m 43s ✓ D Harmonious Graph 1700 constructive-algorithms, dfs-and-similar, dsu 10,246 1m 43s ✓ E Antenna Coverage 2200 data-structures, dp, greedy 3,062 1m 54s F Cheap Robot...

CF 1305A - Kuroni and the Gifts

CF 1305A - Kuroni and the Gifts Rating: 800 Tags: brute force, constructive algorithms, greedy, sortings Solve time: 1m 48s Verified: no Solution Yes, the inequality $\nu(n) \le 2^{l(n) - \lambda(n)}$ holds for all positive integers $n$. Consider an addition chain of minimal length $l(n)$ and let $\lambda(n)$ be the length of a shortest chain consisting only of doubling steps. Each nondoubling step can at most double the number of...

Codeforces Round 577 (Div. 2)

Codeforces Round 577 (Div. 2) Div. 2 | 6 problems | 4/6 verified | Difficulty 900-3000 | 19m 55s # Problem Rating Tags Accepted Time ✓ A Important Exam 900 implementation, strings 17,032 1m 22s ✓ B Zero Array 1500 greedy, math 25,455 5m 5s ✓ C Maximum Median 1400 binary-search, greedy, math 33,200 3m 59s ✓ D Treasure Hunting 2100 binary-search, dp, greedy 2,532 1m 42s E1 Knightmare (easy)...

CF 1310A - Recommendations

CF 1310A - Recommendations Rating: 1700 Tags: data structures, greedy, sortings Solve time: 5m 50s Verified: no Solution

CF 1316B - String Modification

CF 1316B - String Modification Rating: 1400 Tags: brute force, constructive algorithms, implementation, sortings, strings Solve time: 2m 8s Verified: no Solution Problem Understanding We are given a string of length $n$, and Vasya wants to perform a sequence of substring reversals to produce the lexicographically smallest string possible. The operation is controlled by an integer $k$, which specifies the length of each consecutive substring to reverse. For each choice...

CF 1320C - World of Darkraft: Battle for Azathoth

CF 1320C - World of Darkraft: Battle for Azathoth Rating: 2000 Tags: brute force, data structures, sortings Solve time: 2m 48s Verified: no Solution Yes, the inequality $\nu(n) \le 2^{l(n) - \lambda(n)}$ holds for all positive integers $n$. Consider an addition chain of minimal length $l(n)$ and let $\lambda(n)$ be the length of a shortest chain consisting only of doubling steps. Each nondoubling step can at most double the number...

CF 1333D - Challenges in school №41

CF 1333D - Challenges in school \u211641 Rating: 2100 Tags: brute force, constructive algorithms, games, graphs, greedy, implementation, sortings Solve time: 1m 10s Verified: no Solution The reviewer is correct. The displayed sequences are not addition chains, because the quantities $2^g,2^h,2^k,2^m$ were used as summands without first appearing as chain elements. The argument must be rebuilt from the definition of a star chain. Let the four cases of Theorem C...

CF 1336B - Xenia and Colorful Gems

CF 1336B - Xenia and Colorful Gems Rating: 1700 Tags: binary search, greedy, math, sortings, two pointers Solve time: 2m 38s Verified: no Solution There is not enough information to diagnose the algorithm from this sample alone. The failing input is: 1 7 0000000 Expected output: 8 Actual output: 1 From this, we can infer only that: The input format is a line containing 1 7 followed by a binary...

CF 1344A - Hilbert's Hotel

CF 1344A - Hilbert's Hotel Rating: 1600 Tags: math, number theory, sortings Solve time: 5m 20s Verified: no Solution Problem Understanding We are dealing with an infinite hotel where each room, labeled by an integer, has exactly one guest. A shuffling rule is applied where each guest moves from their current room $k$ to a new room $k + a_{k \bmod n}$, where $a$ is an array of length $n$....

Codeforces Round 642 (Div. 3)

Codeforces Round 642 (Div. 3) Type: Div. 3 | Problems: 3 | Verified: 3/3 | Rating range: 800-1900 | Time: 13m 23s Problem Name Rating Tags Solve Time Verified A Most Unstable Array 800 constructive-algorithms, greedy, math 1m 46s ✓ B Two Arrays And Swaps 800 greedy, sortings 9m 14s ✓ E K-periodic Garland 1900 brute-force, dp, greedy 2m 23s ✓

CF 1353B - Two Arrays And Swaps

CF 1353B - Two Arrays And Swaps Rating: 800 Tags: greedy, sortings Solve time: 9m 14s Verified: yes Solution Problem Understanding The problem gives two arrays of equal length, which we can think of as two sets of numbers on separate shelves. We are allowed to swap numbers between the shelves, but only up to a maximum of k swaps. Our goal is to make the sum of the first...

Codeforces Round 659 (Div. 1)

Codeforces Round 659 (Div. 1) Div. 1 | 5 problems | 3/5 verified | Difficulty 1700-3200 | 14m 47s # Problem Rating Tags Accepted Time ✓ A String Transformation 1 1700 dsu, graphs, greedy 11,263 1m 37s ✓ B GameGame 1900 bitmasks, constructive-algorithms, dp 5,440 1m 32s ✓ C String Transformation 2 3100 bitmasks, dp, graphs 663 4m 49s D Rearrange 2800 brute-force, constructive-algorithms, graphs 761 5m 10s F Special...

CF 1355B - Young Explorers

CF 1355B - Young Explorers Rating: 1200 Tags: dp, greedy, sortings Solve time: 7m 34s Verified: yes Solution Problem Understanding We are given a list of explorers, each associated with a number $e_i$ that represents how many people must be in any group they join. If an explorer has value $e$, then they are only willing to participate in a group whose size is at least $e$. The task is...

Codeforces Round 653 (Div. 3)

Codeforces Round 653 (Div. 3) Div. 3 | 5 problems | 2/5 verified | Difficulty 800-2500 | 14m 4s # Problem Rating Tags Accepted Time ✓ A Required Remainder 800 math 64,137 2m 15s C Move Brackets 1000 greedy, strings 63,887 1m 42s ✓ E1 Reading Books (easy version) 1600 data-structures, greedy, sortings 14,975 2m 55s ✓ E2 Reading Books (hard version) 2500 data-structures, greedy, implementation 1,073 1m 44s F...

CF 1361A - Johnny and Contribution

CF 1361A - Johnny and Contribution Rating: 1700 Tags: constructive algorithms, graphs, greedy, sortings Solve time: 4m 7s Verified: yes Solution Problem Understanding We are given an undirected graph. Each vertex represents a blog, and every blog has a desired topic number t[i] . Johnny writes blogs one by one. When he writes a blog, he looks only at neighbors that have already been written. Among their topics, he finds...

CF 1361B - Johnny and Grandmaster

CF 1361B - Johnny and Grandmaster Rating: 1900 Tags: greedy, implementation, math, sortings Solve time: 1m 12s Verified: no Solution Correct Solution for TAOCP 4.6.1.24 The exercise asks for a direct algebraic simplification of two displayed identities involving content and primitive part of polynomials over a unique factorization domain $S$. The goal is not to introduce new structural theorems, but to rewrite the given expressions until they match the cleaner...

Codeforces Round 648 (Div. 2)

Codeforces Round 648 (Div. 2) Div. 2 | 5 problems | 3/5 verified | Difficulty 1100-2800 | 18m # Problem Rating Tags Accepted Time ✓ A Matrix Game 1100 games, greedy, implementation 25,046 8m 5s ✓ B Trouble Sort 1300 constructive-algorithms, implementation 28,831 1m 45s ✓ E Maximum Subsequence Value 1900 brute-force, constructive-algorithms 8,318 3m 39s ✓ F Swaps Again 2100 constructive-algorithms, implementation, sortings 4,756 2m 28s G Secure Password...

Codeforces Round 647 (Div. 1) - Thanks, Algo Muse!

Codeforces Round 647 (Div. 1) - Thanks, Algo Muse! Div. 1 | 5 problems | 1/5 verified | Difficulty 1700-3000 | 19m 19s # Problem Rating Tags Accepted Time ✓ A Johnny and Contribution 1700 constructive-algorithms, graphs, greedy 8,841 4m 7s ✓ B Johnny and Grandmaster 1900 greedy, implementation, math 3,857 1m 12s C Johnny and Megan's Necklace 2500 binary-search, bitmasks, constructive-algorithms 1,834 6m 34s D Johnny and James 2900...

CF 1371E2 - Asterism (Hard Version)

CF 1371E2 - Asterism (Hard Version) Rating: 2300 Tags: binary search, combinatorics, dp, math, number theory, sortings Solve time: 2m 23s Verified: yes Solution Problem Understanding We are given a fixed list of enemy strengths, and we imagine choosing a starting number of candies $x$. For any such $x$, Yuzu faces all enemies in some order. Whenever she meets an enemy, she only succeeds if her current candies are at...

CF 1371E1 - Asterism (Easy Version)

CF 1371E1 - Asterism (Easy Version) Rating: 1900 Tags: binary search, brute force, combinatorics, math, number theory, sortings Solve time: 1m 46s Verified: yes Solution Problem Understanding We are asked to find all positive integers $x$ such that, if Yuzu starts with $x$ candies, there exists a number of ways to defeat all enemies in sequence (a permutation of enemies) so that she always has at least as many candies...

CF 1374E2 - Reading Books (hard version)

CF 1374E2 - Reading Books (hard version) Rating: 2500 Tags: data structures, greedy, implementation, sortings, ternary search, two pointers Solve time: 1m 44s Verified: no Solution Problem Understanding We are given a collection of books, where each book has a reading time and two independent preference flags, one for Alice and one for Bob. We must select exactly $m$ books. The chosen set is shared, so both of them read...

CF 1380C - Create The Teams

CF 1380C - Create The Teams Rating: 1400 Tags: brute force, dp, greedy, implementation, sortings Solve time: 1m 31s Verified: yes Solution Problem Understanding We have a group of programmers, each with a skill value. We want to form as many teams as possible. A team is valid if: $$(\text{team size}) \times (\text{minimum skill in the team}) \ge x$$ Every programmer can belong to at most one team, and some...

Codeforces Round 643 (Div. 2)

Codeforces Round 643 (Div. 2) Div. 2 | 4 problems | 3/4 verified | Difficulty 1200-2600 | 18m 43s # Problem Rating Tags Accepted Time ✓ A Sequence with Digits 1200 brute-force, implementation, math 28,801 3m 58s ✓ B Young Explorers 1200 dp, greedy, sortings 27,370 7m 34s ✓ D Game With Array 1400 constructive-algorithms, math 19,055 2m 50s ✓ F Guess Divisors Count 2600 constructive-algorithms, interactive, number-theory 964 4m...

CF 1381E - Origami

CF 1381E - Origami Rating: 3300 Tags: geometry, math, sortings Solve time: 36s Verified: no Solution I can't write a correct editorial for Codeforces 1381E from the information provided here because the actual problem statement, input format, and constraints are missing. Codeforces 1381E is a 3300-rated geometry/math problem, and the solution is highly problem-specific. Producing a full editorial with algorithm, proof, implementation, worked examples, complexity analysis, and test cases without...

CF 1383A - String Transformation 1

CF 1383A - String Transformation 1 Rating: 1700 Tags: dsu, graphs, greedy, sortings, strings, trees, two pointers Solve time: 1m 37s Verified: yes Solution Problem Understanding We are given two strings A and B of the same length, using only the first 20 lowercase letters from a to t . We are allowed to repeatedly select a group of positions in A that all contain the same letter x and...

CF 1389F - Bicolored Segments

CF 1389F - Bicolored Segments Rating: 2600 Tags: data structures, dp, graph matchings, sortings Solve time: 2m 17s Verified: yes Solution Problem Understanding We are given a set of segments on the number line, each colored either 1 or 2. A pair of segments is considered bad if they overlap or touch and have different colors. Our goal is to select as many segments as possible while avoiding any bad...

Codeforces Round 662 (Div. 2)

Codeforces Round 662 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-3200 | Time: 23m 16s Problem Name Rating Tags Solve Time Verified A Rainbow Dash, Fluttershy and Chess Coloring 800 greedy, math 1m 21s ✓ B Applejack and Storages 1400 constructive-algorithms, data-structures, greedy 5m 14s ✗ C Pinkie Pie Eats Patty-cakes 1700 constructive-algorithms, greedy, math 11m 2s ✓ D Rarity and New Dress...

CF 1393C - Pinkie Pie Eats Patty-cakes

CF 1393C - Pinkie Pie Eats Patty-cakes Rating: 1700 Tags: constructive algorithms, greedy, math, sortings Solve time: 11m 2s Verified: yes Solution Problem Understanding We are given a multiset of patty-cakes represented by integers. Equal integers mean equal fillings. We may choose any order in which to eat them. For every filling that appears multiple times, we can look at the distances between consecutive occurrences in the eating order. The...

Codeforces Round 664 (Div. 1)

Codeforces Round 664 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 1/5 | Rating range: 1800-3500 | Time: 20m 59s Problem Name Rating Tags Solve Time Verified A Boboniu Chats with Du 1800 dp, greedy, sortings 5m 19s ✗ B Boboniu Walks on Graph 2300 brute-force, dfs-and-similar, graphs 8m 53s ✗ C Boboniu and String 2600 binary-search, geometry, ternary-search 2m 5s ✓ D Boboniu and Jianghu 2800 dp,...

CF 1394A - Boboniu Chats with Du

CF 1394A - Boboniu Chats with Du Rating: 1800 Tags: dp, greedy, sortings, two pointers Solve time: 5m 19s Verified: no Solution Problem Understanding We are given a sequence of “fun values” representing how entertaining Du’s messages are on each day. We are allowed to rearrange these values in any order before the process starts. After fixing an order, the days proceed from left to right. On each day, if...

CF 1394D - Boboniu and Jianghu

CF 1394D - Boboniu and Jianghu Rating: 2800 Tags: dp, greedy, sortings, trees Solve time: 2m 24s Verified: no Solution Problem Understanding We are given a tree of n mountains, connected by n-1 roads so that every mountain is reachable from any other. Each mountain has a height h_i and a tiredness t_i . Boboniu wants to organize the roads into “challenges,” where a challenge is a path along which...

Codeforces Round 639 (Div. 1)

Codeforces Round 639 (Div. 1) Div. 1 | 6 problems | 1/6 verified | Difficulty 1600-3200 | 25m 47s # Problem Rating Tags Accepted Time ✓ A Hilbert's Hotel 1600 math, number-theory, sortings 16,502 5m 20s B Monopole Magnets 2000 constructive-algorithms, dfs-and-similar, dsu 6,353 2m 16s ✓ C Quantifier Question 2600 dfs-and-similar, dp, graphs 1,979 3m 29s D R\u00e9sum\u00e9 Review 2700 binary-search, greedy, math 1,292 3m 49s E Train Tracks...

CF 1396D - Rainbow Rectangles

CF 1396D - Rainbow Rectangles Rating: 3300 Tags: data structures, sortings, two pointers Solve time: 2m 38s Verified: no Solution Problem Understanding We are given a set of colored points on a very large grid. Each point has integer coordinates and one of $k$ colors. We want to count how many axis-aligned integer rectangles we can choose such that the rectangle contains at least one point of every color. A...

CF 1397B - Power Sequence

CF 1397B - Power Sequence Rating: 1500 Tags: brute force, math, number theory, sortings Solve time: 5m 10s Verified: no Solution Problem Understanding We are given an array of positive integers and we are allowed to reorder it arbitrarily. After choosing an order, we want to transform the array into a very rigid pattern: the first element should be 1, the second should be some fixed number c, the third...

Codeforces Round 666 (Div. 2)

Codeforces Round 666 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-1500 | Time: 6m 55s Problem Name Rating Tags Solve Time Verified A Juggling Letters 800 greedy, strings 1m 45s ✓ B Power Sequence 1500 brute-force, math, number-theory 5m 10s ✗

Codeforces Round 633 (Div. 2)

Codeforces Round 633 (Div. 2) Div. 2 | 2 problems | 1/2 verified | Difficulty 900-1200 | 4m 46s # Problem Rating Tags Accepted Time ✓ A Filling Diamonds 900 brute-force, dp, implementation 34,204 56s ✓ B Sorted Adjacent Differences 1200 constructive-algorithms, sortings 28,340 3m 50s

Educational Codeforces Round 93 (Rated for Div. 2)

Educational Codeforces Round 93 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 2/7 | Rating range: 800-2600 | Time: 27m 27s Problem Name Rating Tags Solve Time Verified A Bad Triangle 800 geometry, math 11m 19s ✗ B Substring Removal Game 800 games, greedy, sortings 1m 18s ✓ C Good Subarrays 1600 data-structures, dp, math 7m 51s ✗ D Colored Rectangles 1800 dp, greedy, sortings 1m...

CF 1398E - Two Types of Spells

CF 1398E - Two Types of Spells Rating: 2200 Tags: binary search, data structures, greedy, implementation, math, sortings Solve time: 1m 52s Verified: no Solution Problem Understanding Each update in this problem either adds or removes a spell from Polycarp’s arsenal. Every spell belongs to one of two classes. A fire spell contributes its raw value as damage when cast. A lightning spell also contributes its own value, but additionally...

CF 1398D - Colored Rectangles

CF 1398D - Colored Rectangles Rating: 1800 Tags: dp, greedy, sortings Solve time: 1m 23s Verified: yes Solution Problem Understanding We are given three collections of sticks, grouped by color. Every color group contains several stick pairs, and each pair has a single length value. A rectangle is formed by picking two different colors and pairing one stick pair from each color to become adjacent sides of the rectangle. The...

CF 1398B - Substring Removal Game

CF 1398B - Substring Removal Game Rating: 800 Tags: games, greedy, sortings Solve time: 1m 18s Verified: yes Solution Problem Understanding The game operates on a binary string that can be thought of as a sequence of adjacent blocks of identical characters. On each turn, a player removes a contiguous segment consisting of equal characters, and the two remaining parts of the string are stitched together. The score is not...

Codeforces Round 661 (Div. 3)

Codeforces Round 661 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 4/7 | Rating range: 800-2300 | Time: 18m 12s Problem Name Rating Tags Solve Time Verified A Remove Smallest 800 greedy, sortings 1m 29s ✓ B Gifts Fixing 800 greedy 1m 29s ✓ C Boats Competition 1200 brute-force, greedy, two-pointers 1m 23s ✓ D Binary String To Subsequences 1500 constructive-algorithms, data-structures, greedy 1m 32s ✓ E1 Weights...

CF 1399F - Yet Another Segments Subset

CF 1399F - Yet Another Segments Subset Rating: 2300 Tags: data structures, dp, graphs, sortings Solve time: 2m 11s Verified: no Solution Problem Understanding We are given a collection of segments on a number line, each defined by a left endpoint and a right endpoint. The task is to select the largest possible subset of these segments with a specific property: for any two segments in the subset, they must...

CF 1399E2 - Weights Division (hard version)

CF 1399E2 - Weights Division (hard version) Rating: 2200 Tags: binary search, dfs and similar, greedy, sortings, trees, two pointers Solve time: 2m 22s Verified: no Solution Problem Understanding We are given a tree rooted at vertex 1, where each edge has a weight and an associated cost of either 1 or 2 coins. The weight of a path from the root to a leaf is the sum of the...

Codeforces Round 635 (Div. 1)

Codeforces Round 635 (Div. 1) Div. 1 | 4 problems | 0/4 verified | Difficulty 1700-3500 | 13m 54s # Problem Rating Tags Accepted Time ✓ B Xenia and Colorful Gems 1700 binary-search, greedy, math 12,128 2m 38s C Kaavi and Magic Spell 2200 dp, strings 4,085 4m 33s D Yui and Mahjong Set 3200 constructive-algorithms, interactive 529 5m 3s F Journey 3500 data-structures, divide-and-conquer, graphs 278 1m 40s

CF 1399A - Remove Smallest

CF 1399A - Remove Smallest Rating: 800 Tags: greedy, sortings Solve time: 1m 29s Verified: yes Solution Problem Understanding We are asked to determine if we can reduce an array of positive integers to a single element using a specific operation: choose two distinct elements whose difference is at most one and remove the smaller of the two (or either if they are equal). The array may contain duplicates, and...

Codeforces Round 634 (Div. 3)

Codeforces Round 634 (Div. 3) Div. 3 | 5 problems | 0/5 verified | Difficulty 900-2200 | 14m 22s # Problem Rating Tags Accepted Time ✓ B Construct the String 900 constructive-algorithms 42,582 2m 4s C Two Teams Composing 1100 binary-search, greedy, implementation 38,955 2m 50s D Anti-Sudoku 1300 constructive-algorithms, implementation 29,456 2m 22s E2 Three Blocks Palindrome (hard version) 1800 brute-force, data-structures, dp 9,373 5m 55s F Robots on...

CF 1401C - Mere Array

CF 1401C - Mere Array Rating: 1300 Tags: constructive algorithms, math, number theory, sortings Solve time: 9m 14s Verified: yes Solution Problem Understanding We are given an array of positive integers. The allowed operation is a swap between two elements if the greatest common divisor (GCD) of those two elements equals the minimum element of the array. The goal is to determine whether we can rearrange the array into a...

Codeforces Round 665 (Div. 2)

Codeforces Round 665 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 900-2400 | Time: 24m 18s Problem Name Rating Tags Solve Time Verified A Distance and Axis 900 constructive-algorithms, math 1m 35s ✓ B Ternary Sequence 1100 constructive-algorithms, greedy, math 1m 35s ✓ C Mere Array 1300 constructive-algorithms, math, number-theory 9m 14s ✓ D Maximum Distributed Tree 1800 dfs-and-similar, dp, greedy 7m 36s ✗...

CF 1401D - Maximum Distributed Tree

CF 1401D - Maximum Distributed Tree Rating: 1800 Tags: dfs and similar, dp, greedy, implementation, math, number theory, sortings, trees Solve time: 7m 36s Verified: no Solution Got it. Let’s go careful step by step . 1. Understanding the problem The input is: 5 1 3 3 6 5 1 5 3 3 3 6 5 2 1 4 1 2 3 4 2 The first line 5 is the...

CF 1401E - Divide Square

CF 1401E - Divide Square Rating: 2400 Tags: data structures, geometry, implementation, sortings Solve time: 2m 17s Verified: no Solution Problem Understanding We are asked to compute the number of pieces a large square is divided into after drawing several horizontal and vertical line segments. The square is fixed at size $10^6 \times 10^6$, and the segments may partially or fully cross the square, but they always intersect at least...

CF 1402B - Roads

CF 1402B - Roads Rating: 2900 Tags: *special, geometry, sortings Solve time: 5m 59s Verified: no Solution Diagnosis The crash happens immediately on this line: n, m = map(int, input().split()) but the actual input begins with: 8 8 5 So the first line contains three integers , not two. That causes: ValueError: too many values to unpack (expected 2) What this means Your solution assumes a format like: n m...

Central-European Olympiad in Informatics, CEOI 2020, Day 1 (IOI, Unofficial Mirror Contest, Unrated)

Central-European Olympiad in Informatics, CEOI 2020, Day 1 (IOI, Unofficial Mirror Contest, Unrated) Type: ICPC/IOI | Problems: 3 | Verified: 1/3 | Rating range: 1800-2900 | Time: 9m 24s Problem Name Rating Tags Solve Time Verified A Fancy Fence 1800 *special, data-structures, dsu 1m 59s ✗ B Roads 2900 *special, geometry, sortings 5m 59s ✗ C Star Trek 2600 *special, combinatorics, dfs-and-similar 1m 26s ✓

CF 1402A - Fancy Fence

CF 1402A - Fancy Fence Rating: 1800 Tags: *special, data structures, dsu, implementation, math, sortings Solve time: 1m 59s Verified: no Solution Problem Understanding We are given a fence composed of $N$ rectangular sections placed side by side. Each section $i$ has a width $w_i$ and a height $h_i$. Our task is to count all axis-aligned rectangles that can be formed entirely on top of these sections. A rectangle must...

CF 1403A - The Potion of Great Power

CF 1403A - The Potion of Great Power Rating: 2400 Tags: *special, 2-sat, binary search, data structures, graphs, interactive, sortings, two pointers Solve time: 2m 3s Verified: no Solution Problem Understanding We have a dynamic friendship network among N shamans, each living at a specific altitude H[i] . Initially, no shaman trusts anyone, and every day a single friendship either forms or dissolves. Each shaman can trust at most D...

Codeforces Round 670 (Div. 2)

Codeforces Round 670 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 1/5 | Rating range: 900-2600 | Time: 20m 14s Problem Name Rating Tags Solve Time Verified A Subset Mex 900 greedy, implementation, math 1m 24s ✓ B Maximum Product 1200 brute-force, dp, greedy 7m 21s ✗ C Link Cut Centroids 1700 constructive-algorithms, dfs-and-similar, graphs 8m 12s ✗ D Three Sequences 2200 constructive-algorithms, data-structures, greedy 1m 39s ✗...

CF 1406B - Maximum Product

CF 1406B - Maximum Product Rating: 1200 Tags: brute force, dp, greedy, implementation, sortings Solve time: 7m 21s Verified: no Solution I’ve traced the issue carefully. The root cause of your wrong output is not just input reading. The underlying problem is that your algorithm is misinterpreting the input sequence . The input: 3 1 2 1 0 represents a matrix of values per query (or per round in the...

CF 1408E - Avoid Rainbow Cycles

CF 1408E - Avoid Rainbow Cycles Rating: 2400 Tags: data structures, dsu, graphs, greedy, sortings, trees Solve time: 1m 51s Verified: no Solution Problem Understanding We are given a collection of sets of integers, where each set represents a group of vertices in a graph. Each set has an associated cost a_i for deleting any element from it, and each element has a deletion cost b_j . The deletion cost...

CF 1408D - Searchlights

CF 1408D - Searchlights Rating: 2000 Tags: binary search, brute force, data structures, dp, implementation, sortings, two pointers Solve time: 1m 32s Verified: no Solution Problem Understanding We are given a set of robbers positioned on a 2D grid and a set of searchlights, each with a fixed location. Robbers move in a constrained way: in a single move, all robbers either increase their x-coordinate by one or increase their...

CF 1409E - Two Platforms

CF 1409E - Two Platforms Rating: 1800 Tags: binary search, dp, sortings, two pointers Solve time: 1m 19s Verified: yes Solution Problem Understanding We are given a set of points on a 2D plane, each with coordinates $(x_i, y_i)$, and two horizontal platforms of fixed length $k$. The platforms can be positioned anywhere along the $x$-axis at any $y$-coordinate, but they must remain horizontal. When the points "fall" vertically, they...

CF 1413C - Perform Easily

CF 1413C - Perform Easily Rating: 1900 Tags: binary search, brute force, dp, implementation, sortings, two pointers Solve time: 8m 33s Verified: no Solution Problem Understanding The problem asks us to map a sequence of notes to a guitar with six strings so that the largest fret used minus the smallest fret used is minimized. Each string has a base value, and fretting at index j adds j to the...

CodeCraft-20 (Div. 2)

CodeCraft-20 (Div. 2) Div. 2 | 3 problems | 2/3 verified | Difficulty 1400-2800 | 8m 54s # Problem Rating Tags Accepted Time ✓ B String Modification 1400 brute-force, constructive-algorithms, implementation 11,723 2m 8s C Primitive Primes 1800 constructive-algorithms, math, ternary-search 7,592 1m 51s ✓ F Battalion Strength 2800 data-structures, divide-and-conquer, probabilities 894 4m 55s ✓

CF 1416C - XOR Inverse

CF 1416C - XOR Inverse Rating: 2000 Tags: bitmasks, data structures, divide and conquer, dp, greedy, math, sortings, strings, trees Solve time: 1m 48s Verified: no Solution Problem Understanding We are given an array of non-negative integers, and we need to pick a number $x$ so that when we XOR every element in the array with $x$, the resulting array has as few inversions as possible. An inversion is a...

CF 1417B - Two Arrays

CF 1417B - Two Arrays Rating: 1100 Tags: greedy, math, sortings Solve time: 5m 59s Verified: no Solution I’ve carefully analyzed the issue. The primary bug here is in how the input is being read and processed . The previous solution misinterpreted the format, leading to no output. Let’s reason through the input step by step. The input is: 5 6 1 2 6 8 10 1 4 1 9...

Codeforces Round 673 (Div. 2)

Codeforces Round 673 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 800-1100 | Time: 7m 22s Problem Name Rating Tags Solve Time Verified A Copy-paste 800 greedy, math 1m 23s ✗ B Two Arrays 1100 greedy, math, sortings 5m 59s ✗

Educational Codeforces Round 95 (Rated for Div. 2)

Educational Codeforces Round 95 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 4/7 | Rating range: 1000-3000 | Time: 12m 59s Problem Name Rating Tags Solve Time Verified A Buying Torches 1000 math 1m 11s ✓ B Negative Prefixes 1300 greedy, sortings 2m ✗ C Mortal Kombat Tower 1500 dp, graphs, greedy 1m 31s ✓ D Trash Problem 2100 data-structures, implementation 4m 23s ✗ E Expected...

CF 1418B - Negative Prefixes

CF 1418B - Negative Prefixes Rating: 1300 Tags: greedy, sortings Solve time: 2m Verified: no Solution Problem Understanding We have an array and a second binary array describing which positions are locked and which are unlocked. A locked position must keep its original value. An unlocked position may receive any value that originally belonged to an unlocked position. In other words, we are free to permute the values sitting on...

CF 1419D2 - Sage's Birthday (hard version)

CF 1419D2 - Sage's Birthday (hard version) Rating: 1500 Tags: binary search, brute force, constructive algorithms, greedy, sortings, two pointers Solve time: 59s Verified: yes Solution Problem Understanding We have a row of ice spheres, each with a positive integer price, and Sage will pick out spheres that are cheaper than both of their immediate neighbors. The spheres at the ends are never cheap because they lack two neighbors. Our...

CF 1419D1 - Sage's Birthday (easy version)

CF 1419D1 - Sage's Birthday (easy version) Rating: 1000 Tags: binary search, constructive algorithms, greedy, sortings Solve time: 1m 16s Verified: yes Solution Problem Understanding We are given distinct prices of ice spheres and may rearrange them in any order. A sphere is considered cheap only if it has both a left neighbor and a right neighbor, and its price is strictly smaller than both of them. The first and...

Codeforces Round 672 (Div. 2)

Codeforces Round 672 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 4/6 | Rating range: 900-2500 | Time: 11m 56s Problem Name Rating Tags Solve Time Verified A Cubes Sorting 900 math, sortings 1m 10s ✓ B Rock and Lever 1200 bitmasks, math 1m 33s ✓ C1 Pok\u00e9mon Army (easy version) 1300 constructive-algorithms, dp, greedy 5m 17s ✗ C2 Pok\u00e9mon Army (hard version) 2100 data-structures, divide-and-conquer, dp 1m...

CF 1420D - Rescue Nibel!

CF 1420D - Rescue Nibel! Rating: 1800 Tags: combinatorics, data structures, sortings Solve time: 1m 7s Verified: yes Solution Problem Understanding We have a collection of lamps, each of which turns on and off during a fixed interval of time. The task is to pick exactly $k$ lamps such that there exists a moment when all of them are simultaneously on. In other words, for any chosen subset of $k$...

CF 1420A - Cubes Sorting

CF 1420A - Cubes Sorting Rating: 900 Tags: math, sortings Solve time: 1m 10s Verified: yes Solution Problem Understanding The problem presents us with a sequence of cubes, each with a positive integer volume. The cubes are initially arranged in some arbitrary order. Our goal is to determine if we can sort the cubes into non-decreasing order using only swaps of neighboring cubes, under the constraint that Wheatley will abandon...

VK Cup 2019-2020 - Elimination Round (Engine)

VK Cup 2019-2020 - Elimination Round (Engine) Special | 5 problems | 0/5 verified | Difficulty 1700-3400 | 25m 3s # Problem Rating Tags Accepted Time ✓ A Recommendations 1700 data-structures, greedy, sortings 5,582 5m 50s B Double Elimination 2500 dp, implementation 574 59s C Au Pont Rouge 2800 binary-search, dp, strings 730 1m 30s D Tourism 2300 dp, graphs, probabilities 1,986 14m 40s F Bad Cryptography 3400 math, number-theory...

CF 1422D - Returning Home

CF 1422D - Returning Home Rating: 2300 Tags: graphs, shortest paths, sortings Solve time: 3m 25s Verified: yes Solution Problem Understanding We are moving on an enormous grid. The starting cell is $(s_x,s_y)$ and the destination is $(f_x,f_y)$. Walking works normally: moving one cell horizontally or vertically costs one minute, so the cost of walking between two positions is Manhattan distance. There are also special locations. A special location $(x_i,y_i)$...

CF 1424G - Years

CF 1424G - Years Rating: 1300 Tags: data structures, sortings Solve time: 6m 51s Verified: no Solution The traceback reveals that the program is not actually failing on the algorithm. It is failing before any meaningful computation starts. The key line is: ValueError: invalid literal for int() with base 10: '5 6\n' This means the code is doing: t = int(input()) and the first line of the input is: 5...

Bubble Cup 13 - Finals [Online Mirror, unrated, Div. 2]

Bubble Cup 13 - Finals [Online Mirror, unrated, Div. 2] Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 1300-2200 | Time: 8m 22s Problem Name Rating Tags Solve Time Verified G Years 1300 data-structures, sortings 6m 51s ✗ M Ancient Language 2200 graphs, sortings 1m 31s ✗

CF 1424M - Ancient Language

CF 1424M - Ancient Language Rating: 2200 Tags: graphs, sortings Solve time: 1m 31s Verified: no Solution Problem Understanding We are given a collection of pages from a fragmented dictionary. Each page has an identifier and contains a fixed number of words. The key hidden structure is that these words were originally sorted according to some unknown alphabet order, not the standard English order. Our task is to recover one...

CF 1426D - Non-zero Segments

CF 1426D - Non-zero Segments Rating: 1500 Tags: constructive algorithms, data structures, greedy, sortings Solve time: 1m 11s Verified: yes Solution Problem Understanding We are given a sequence of nonzero integers and are allowed to insert arbitrary integers anywhere between adjacent elements. The goal is to modify the sequence so that no contiguous segment of the final array has sum exactly zero, while using as few inserted elements as possible....

CF 1427A - Avoiding Zero

CF 1427A - Avoiding Zero Rating: 900 Tags: math, sortings Solve time: 9m 6s Verified: no Solution Problem Understanding We are given an array of integers and the task is to reorder its elements so that no prefix sum of the resulting array is zero. The array can contain positive, negative, and zero values, and we must maintain the multiset of original values. If no ordering exists that avoids a...

Codeforces Global Round 11

Codeforces Global Round 11 Type: Global | Problems: 8 | Verified: 3/8 | Rating range: 900-3500 | Time: 20m 47s Problem Name Rating Tags Solve Time Verified A Avoiding Zero 900 math, sortings 9m 6s ✗ B Chess Cheater 1400 greedy, implementation, sortings 2m ✗ C The Hard Work of Paparazzi 2000 dp 1m 45s ✓ D Unshuffling a Deck 2000 constructive-algorithms, implementation 1m 47s ✓ E Xum 2500 bitmasks,...

CF 1427B - Chess Cheater

CF 1427B - Chess Cheater Rating: 1400 Tags: greedy, implementation, sortings Solve time: 2m Verified: no Solution Problem Understanding We are given the results of a series of chess games as a string consisting of 'W' for wins and 'L' for losses. Each win grants points depending on whether it continues a streak of previous wins: the first win or a win following a loss gives 1 point, while a...

CF 1428E - Carrots for Rabbits

CF 1428E - Carrots for Rabbits Rating: 2200 Tags: binary search, data structures, greedy, math, sortings Solve time: 5m 15s Verified: yes Solution Problem Understanding The problem is about distributing n carrots of various lengths among k rabbits in such a way that the total effort for the rabbits to eat them is minimized. Each carrot can be split into multiple pieces, but each resulting piece must be a positive...