#games

CF 980C - Posterized Rating: 1700 Tags: games, greedy Model: gpt-5-3-mini Solve time: 1m 7s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a33a56a-75ec-83ec-8c82-16909b3df43c Solution Problem Understanding We are given a sequence of pixel intensities, each an integer between 0 and 255. The task is to “simplify” this sequence by first partitioning the entire value range $[0, 255]$ into contiguous segments. Each segment has length at most $k$, and every integer in the...

CF 930D - Game with Tokens Rating: 2500 Tags: data structures, games, implementation Model: gpt-5-3-mini Solve time: 1m 49s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a32759f-eca8-83ec-8ce0-6915f5e36d45 Solution Problem Understanding We are given a set of black tokens placed at distinct integer grid points. There is also a single white token whose starting position is not fixed. The game proceeds in alternating turns: white moves first, and on each turn a player...

CF 896B - Ithea Plays With Chtholly Rating: 2000 Tags: binary search, constructive algorithms, games, greedy, interactive Model: gpt-5-3-mini Solve time: 3m 12s Verified: yes (1/1 samples) Solution Problem Understanding We are maintaining a row of n positions, each initially empty. Over time, we receive a sequence of m numbers. After each number arrives, we must immediately assign it to one of the n positions, possibly overwriting what was there...

Codeforces Round 462 (Div. 2)

Codeforces Round 462 (Div. 2) Div. 2 | 2 problems | 2/2 verified | Difficulty 1200-1400 | 2m 40s # Problem Rating Tags Accepted Time ✓ A A Compatible Pair 1400 brute-force, games 7,600 1m 8s ✓ B A Prosperous Lot 1200 constructive-algorithms, implementation 9,163 1m 32s ✓

CF 934A - A Compatible Pair

CF 934A - A Compatible Pair Rating: 1400 Tags: brute force, games Solve time: 1m 8s Verified: yes Solution Problem Understanding Two players are interacting with two arrays of integers. One player owns an array of length n, the other owns an array of length m. Each number represents a lantern’s brightness, and brightness can be positive, negative, or zero. The interaction is adversarial. First, the first player permanently removes...

Codeforces Round 467 (Div. 1)

Codeforces Round 467 (Div. 1) Div. 1 | 2 problems | 0/2 verified | Difficulty 2100-2300 | 4m 52s # Problem Rating Tags Accepted Time ✓ B Sleepy Game 2100 dfs-and-similar, dp, games 3,411 1m 40s C Lock Puzzle 2300 constructive-algorithms, implementation, strings 1,259 3m 12s

CF 936B - Sleepy Game

CF 936B - Sleepy Game Rating: 2100 Tags: dfs and similar, dp, games, graphs Solve time: 1m 40s Verified: no Solution Problem Understanding We are given a directed graph where each vertex represents a state of a game token. A token starts at a fixed vertex, and two players alternate moving it along outgoing edges. A player loses immediately if they are to move from a vertex that has no...

Codeforces Round 473 (Div. 2)

Codeforces Round 473 (Div. 2) Div. 2 | 3 problems | 3/3 verified | Difficulty 800-1900 | 4m 23s # Problem Rating Tags Accepted Time ✓ A Mahmoud and Ehab and the even-odd game 800 games, math 55,647 58s ✓ C Mahmoud and Ehab and the wrong algorithm 1500 constructive-algorithms, trees 6,207 1m 13s ✓ E Mahmoud and Ehab and the xor-MST 1900 bitmasks, dp, graphs 3,765 2m 12s ✓

CF 959A - Mahmoud and Ehab and the even-odd game

CF 959A - Mahmoud and Ehab and the even-odd game Rating: 800 Tags: games, math Solve time: 58s Verified: yes Solution Problem Understanding The game starts with a single integer value, and two players alternately reduce it. On Mahmoud’s turn, he is only allowed to subtract an even positive number that does not exceed the current value. On Ehab’s turn, he is only allowed to subtract an odd positive number...

CF 1033G - Chip Game

CF 1033G - Chip Game Rating: 3500 Tags: games Solve time: 5m 35s Verified: no Solution Problem Understanding We are given several independent piles of chips. Each pile has a large initial size, and two players, Alice and Bob, first choose how many chips they will remove per move, denoted by a and b . After these choices, they play a turn-based game on all piles combined. On Alice’s turn,...

CF 1033C - Permutation Game

CF 1033C - Permutation Game Rating: 1600 Tags: brute force, dp, games Solve time: 11m 39s Verified: yes Solution Problem Understanding We are given a permutation of values placed on a line of positions from 1 to n. A token starts on any chosen position, and two players alternate moving it. A move is only legal if we jump from position i to position j where the value strictly increases,...

CF 1037G - A Game on Strings

CF 1037G - A Game on Strings Rating: 3200 Tags: games Solve time: 5m 37s Verified: yes Solution Problem Understanding We are given a base string and then asked to answer many independent games played on substrings of it. Each game starts from a chosen segment of the string, and two players alternate turns. A move consists of picking a character that appears in the current string state, deleting every...

CF 1375F - Integer Game

CF 1375F - Integer Game Rating: 2600 Tags: constructive algorithms, games, interactive, math Solve time: 6m 23s Verified: no Solution Problem Understanding Three numbers represent the sizes of three piles of stones. The interaction alternates between us and the opponent. On our turn we output a positive integer y , and on the opponent’s turn they must add exactly y stones to one of the three piles, with the restriction...

Educational Codeforces Round 90 (Rated for Div. 2)

Educational Codeforces Round 90 (Rated for Div. 2) Div. 2 | 4 problems | 1/4 verified | Difficulty 900-2400 | 16m 42s # Problem Rating Tags Accepted Time ✓ A Donut Shops 1000 greedy, implementation, math 29,473 4m 37s B 01 Game 900 games 52,643 2m 24s ✓ E Sum of Digits 2200 brute-force, constructive-algorithms, dp 2,951 7m 2s F Network Coverage 2400 binary-search, constructive-algorithms, data-structures 1,878 2m 39s

CF 1373B - 01 Game

CF 1373B - 01 Game Rating: 900 Tags: games Solve time: 2m 24s Verified: yes Solution Problem Understanding We are given a binary string and two players who alternately remove exactly two adjacent characters from it. Each move deletes a contiguous pair, so the string shrinks by 2 characters each turn. A player loses immediately when they are faced with a string where no adjacent pair exists, which happens when...

CF 1369F - BareLee

CF 1369F - BareLee Rating: 2700 Tags: dfs and similar, dp, games Solve time: 3m 19s Verified: yes Solution Problem Understanding Each round is a two-player deterministic game played on a single integer. A round starts with a value $s_i$ on a board and a limit $e_i$. Players alternate turns, and on each turn the current value $a$ must be replaced by either $a+1$ or $2a$. If a player ever...

CF 1368F - Lamps on a Circle

CF 1368F - Lamps on a Circle Rating: 2600 Tags: games, implementation, interactive, math Solve time: 2m 16s Verified: yes Solution Problem Understanding We are playing an interactive game on a circular array of n positions. All positions start empty. On each turn, the player is allowed to pick a number k and activate any k positions. Immediately after that, an adversary removes a block of exactly k consecutive positions...

CF 1221E - Game With String

CF 1221E - Game With String Rating: 2500 Tags: games Solve time: 2m 11s Verified: no Solution Problem Understanding We are given a binary string made of two types of characters: empty cells denoted by . and blocked cells denoted by X . Two players alternate turns, starting with Alice. Each move consists of choosing a contiguous segment of exactly fixed length and converting every character in that segment into...

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 1100D - Dasha and Chess

CF 1100D - Dasha and Chess Rating: 2500 Tags: constructive algorithms, games, interactive Solve time: 9m 7s Verified: no Solution Problem Understanding We are simulating an interaction on a 999 by 999 grid with a single white king and many black rooks. The king moves first and can step to any of the eight neighboring cells. After each king move, an adversary moves exactly one rook to any empty square,...

CF 1099F - Cookies

CF 1099F - Cookies Rating: 2400 Tags: binary search, data structures, dfs and similar, dp, games, trees Solve time: 6m 43s Verified: no Solution Problem Understanding We are given a rooted tree where each vertex contains a pile of cookies. Every vertex also has a cost for eating one cookie at that vertex, and every edge from a node to its parent has a cost for moving upward along it....

CF 1076G - Array Game

CF 1076G - Array Game Rating: 3000 Tags: data structures, games Solve time: 8m 11s Verified: no Solution Problem Understanding We are given a one-dimensional board where each cell contains a positive number of tokens. A chip starts on the left boundary of a chosen segment, and players alternate moves. On a move, the player must spend one token in some cell within a limited forward window from the chip’s...

Bubble Cup 14 - Finals Online Mirror (Unrated, ICPC Rules, Teams Preferred, Div. 2)

Bubble Cup 14 - Finals Online Mirror (Unrated, ICPC Rules, Teams Preferred, Div. 2) Div. 2 | 3 problems | 3/3 verified | Difficulty 1400-2300 | 5m 40s # Problem Rating Tags Accepted Time ✓ E Array Game 1900 games, greedy, two-pointers 2,382 1m 34s ✓ F Party Organization 2300 brute-force, math, probabilities 615 2m 22s ✓ J Robot Factory 1400 bitmasks, dfs-and-similar 4,417 1m 44s ✓

CF 1600E - Array Game

CF 1600E - Array Game Rating: 1900 Tags: games, greedy, two pointers Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given an array of numbers laid out in a line. Two players alternate turns, starting with Alice. On each move, a player removes either the leftmost or rightmost remaining element and appends it to a sequence that is being constructed. The only restriction is that the resulting...

CF 1773I - Interactive Factorial Guessing

CF 1773I - Interactive Factorial Guessing Rating: 2500 Tags: brute force, games, implementation, interactive Solve time: 2m 18s Verified: no Solution Problem Understanding We are interacting with a hidden integer $n$, but we are not allowed to see it directly. Instead, we can ask up to 10 questions of the form: “what is the $k$-th digit from the right of $n!$ in decimal representation?”. If that digit does not exist...

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 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 1728D - Letter Picking

CF 1728D - Letter Picking Rating: 1800 Tags: constructive algorithms, dp, games, two pointers Solve time: 6m 16s Verified: yes Solution Problem Understanding We are playing a two-player game on a string that behaves like a deque. The string initially contains lowercase letters and has even length. Alice moves first, and players alternate. On each turn, the player removes either the leftmost or rightmost character of the current string and...

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 1404B - Tree Tag

CF 1404B - Tree Tag Rating: 1900 Tags: dfs and similar, dp, games, trees Solve time: 3m 37s Verified: yes Solution Problem Understanding We are given a tree where two players start on different vertices. Alice moves first. On each turn, Alice can jump to any vertex within distance da , and Bob can jump to any vertex within distance db . Distance is standard shortest path length in the...

CF 1370C - Number Game Rating: 1400 Tags: games, math, number theory Model: gpt-5-5 Solve time: 4m 3s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e52c3-f374-83ec-8a3c-fb04c12ded07 Solution Problem Understanding We are playing a two-player turn-based game starting from a single integer. On each move, the current player transforms the number using one of two operations: either subtract one from it, or divide it by some odd divisor greater than one. The divisor...

CF 1346H - Game with Segments Rating: 2700 Tags: *special, data structures, games Model: gpt-5-3-mini Solve time: 2m 21s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e23b1-4140-83ec-9c31-41f2c214dfd1 Solution Problem Understanding We are given an interval on a number line as a starting position, and a collection of special target intervals called terminal segments. A move consists of shrinking the current interval by exactly one unit from either the left side or the...

CF 1382B - Sequential Nim Rating: 1100 Tags: dp, games Model: gpt-5-3-mini Solve time: 4m 43s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e6ef5-142c-83ec-96d7-74def36b8cb3 Solution Problem Understanding The game is played on a row of piles. On each move, only the leftmost pile that still contains stones matters, and the player may remove any positive number of stones from that pile. Once a pile becomes empty, play continues with the next pile...

CF 1312F - Attack on Red Kingdom Rating: 2500 Tags: games, two pointers Model: gpt-5-3-mini Solve time: 3m 57s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2de030-9178-83ec-ba86-efd9bfd613fa Solution Problem Understanding We are given a row of castles, each starting with some number of soldiers. Two players alternate turns, starting with the White King, and each turn consists of choosing a castle and applying one of three attack types that reduce the number...

CF 1372D - Omkar and Circle Rating: 2100 Tags: brute force, dp, games, greedy Model: gpt-5-3-mini Solve time: 3m 34s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e5767-64e8-83ec-a632-db49be3629d1 Solution Problem Understanding We start with a circular arrangement of numbers. Each move takes one position on the circle, replaces that position with the sum of its two neighbors, and removes those two neighbors. The circle shrinks by two elements each time, and we...

CF 1215D - Ticket Game

CF 1215D - Ticket Game Rating: 1700 Tags: games, greedy, math Solve time: 8m Verified: no Solution Problem Understanding We are given a ticket represented by a string of even length. Each position corresponds to a digit from 0 to 9, except that some positions are unknown and marked with a question mark. The unknown positions must eventually be filled with digits. Two players take turns filling these unknown positions,...

CF 1197F - Coloring Game

CF 1197F - Coloring Game Rating: 2700 Tags: dp, games, matrices Solve time: 5m 41s Verified: no Solution Problem Understanding Each strip can be viewed as a line of positions, and each position holds a chip. A chip starts at the rightmost cell of its strip, and players alternately move exactly one chip per turn, pushing it left by 1, 2, or 3 positions, as long as the move stays...

Educational Codeforces Round 68 (Rated for Div. 2)

Educational Codeforces Round 68 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 4/7 | Rating range: 800-2700 | Time: 29m 26s Problem Name Rating Tags Solve Time Verified A Remove a Progression 800 math 4m 23s ✗ B Yet Another Crosses Problem 1300 implementation 3m 1s ✓ C From S To T 1300 implementation, strings 1m 41s ✓ D 1-2-K Game 1700 games, math 6m 6s...

CF 1194D - 1-2-K Game

CF 1194D - 1-2-K Game Rating: 1700 Tags: games, math Solve time: 6m 6s Verified: no Solution Problem Understanding We are given a single chip placed at the right end of a linear strip of cells indexed from 0 up to n. Two players alternate moves starting from the rightmost position n, and each move consists of shifting the chip left by exactly 1, 2, or k positions, as long...

Codeforces Round 573 (Div. 1)

Codeforces Round 573 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 4/6 | Rating range: 1400-3400 | Time: 34m 45s Problem Name Rating Tags Solve Time Verified A Tokitsukaze and Discard Items 1400 implementation, two-pointers 13m 11s ✗ B Tokitsukaze, CSL and Stone Game 1800 games 3m 6s ✓ C Tokitsukaze and Duel 2300 brute-force, games, greedy 4m 20s ✓ D Tokitsukaze and Strange Rectangle 2000 data-structures, divide-and-conquer,...

CF 1190C - Tokitsukaze and Duel

CF 1190C - Tokitsukaze and Duel Rating: 2300 Tags: brute force, games, greedy Solve time: 4m 20s Verified: yes Solution Problem Understanding We are given a binary string representing a line of cards, each showing either 0 or 1. A move consists of choosing exactly k consecutive positions and forcing all of them to become identical, either all 0 or all 1. The rest of the array is unchanged. Two...

Codecraft-18 and Codeforces Round 458 (Div. 1 + Div. 2, combined)

Codecraft-18 and Codeforces Round 458 (Div. 1 + Div. 2, combined) Div. 1+2 | 8 problems | 6/8 verified | Difficulty 900-3400 | 38m 3s # Problem Rating Tags Accepted Time ✓ A Perfect Squares 900 brute-force, implementation, math 15,720 4m 38s ✓ B Conan and Agasa play a Card Game 1200 games, greedy, implementation 9,058 2m 35s ✓ C Travelling Salesman and Special Numbers 1800 brute-force, combinatorics, dp 4,209...

CF 1102C - Doors Breaking and Repairing

CF 1102C - Doors Breaking and Repairing Rating: 1200 Tags: games Solve time: 5m 1s Verified: yes Solution Problem Understanding We are given a collection of doors, each with an initial durability value. You and an opponent alternate moves for an extremely large number of turns, so the process effectively runs until both players’ optimal strategies stabilize. On your turn, you choose a door and damage it by a fixed...

CF 1091H - New Year and the Tricolore Recreation

CF 1091H - New Year and the Tricolore Recreation Rating: 3200 Tags: games Solve time: 9m 40s Verified: yes Solution Problem Understanding Each row contains three ordered tokens on an infinite number line: a blue token on the left, a white token in the middle, and a red token on the right. The relative order inside each row must always remain strictly blue < white < red, and no two...

CF 1090G - Combostone

CF 1090G - Combostone Rating: 2500 Tags: games, implementation Solve time: 2m 45s Verified: yes Solution Problem Understanding We are given a configuration of stones arranged in a line. Each stone carries some information, and the game is played by two players who alternate moves. A move consists of selecting two adjacent stones, removing them, and replacing them with a single new stone whose type is determined by a fixed...

CF 919F - A Game With Numbers

CF 919F - A Game With Numbers Rating: 2600 Tags: games, graphs, shortest paths Solve time: 5m 51s Verified: yes Solution Problem Understanding We are given a two-player game where Alice and Bob each hold 8 cards with numbers from 0 to 4. On a player’s turn, they select one of their cards with a non-zero number and one of the opponent’s cards with a non-zero number, add them modulo...

CF 917B - MADMAX

CF 917B - MADMAX Rating: 1700 Tags: dfs and similar, dp, games, graphs Solve time: 4m 34s Verified: no Solution Problem Understanding We are given a directed acyclic graph where each edge carries a lowercase letter. Two tokens start on possibly different vertices: one belongs to Max and one to Lucas. They take turns moving their own token along outgoing edges, and the twist is that the letters along the...

CF 914H - Ember and Storm's Tree Game

CF 914H - Ember and Storm's Tree Game Rating: 3400 Tags: combinatorics, dp, games, trees Solve time: 10m 4s Verified: yes Solution Problem Understanding The game begins with Ember choosing a tree on $n$ labeled vertices, with the restriction that no vertex has degree exceeding $d$. After that, Storm selects an ordered pair of vertices $(u, v)$, which determines a simple path in the tree. Writing the vertex labels along...

CF 914B - Conan and Agasa play a Card Game

CF 914B - Conan and Agasa play a Card Game Rating: 1200 Tags: games, greedy, implementation Solve time: 2m 35s Verified: yes Solution Problem Understanding We have a game where Conan and Agasa take turns removing cards from a pile. Each card has a positive integer written on it. When a player chooses a card, not only does that card get removed, but all cards with strictly smaller numbers are...

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 1110G - Tree-Tac-Toe

CF 1110G - Tree-Tac-Toe Rating: 3100 Tags: constructive algorithms, games, trees Solve time: 1m 4s Verified: yes Solution Problem Understanding We are asked to analyze a game of tic-tac-toe played on a tree. Each vertex is either uncolored or already white. Two players alternate coloring vertices, starting with white. The first player to complete a path of three vertices in their color wins. If all vertices are colored without a...

Forethought Future Cup - Final Round (Onsite Finalists Only)

Forethought Future Cup - Final Round (Onsite Finalists Only) Type: Special | Problems: 6 | Verified: 2/6 | Rating range: 1500-3500 | Time: 9m 37s Problem Name Rating Tags Solve Time Verified A Hide and Seek 1500 graphs 1m 51s ✗ B Chladni Figure 1900 brute-force, strings 1m 2s ✓ C Thanos Nim 2000 games 1m 22s ✓ D Palindrome XOR 2400 dfs-and-similar, graphs 1m 45s ✗ E Rainbow Coins...

CF 1147F - Zigzag Game

CF 1147F - Zigzag Game Rating: 3500 Tags: games, interactive Solve time: 1m 44s Verified: no Solution Problem Understanding The game is played on a complete bipartite graph with two equal groups of vertices. Every vertex on the left side connects to every vertex on the right side, and each such edge has a unique weight. The input gives these weights as an $n \times n$ matrix, where entry $a_{ij}$...

CF 1147C - Thanos Nim

CF 1147C - Thanos Nim Rating: 2000 Tags: games Solve time: 1m 22s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game played on an array of piles, each containing some number of stones. There are $n$ piles, and $n$ is guaranteed to be even. Alice moves first, and on each turn a player must choose exactly $n/2$ nonempty piles and remove at least one stone...

CF 1149E - Election Promises

CF 1149E - Election Promises Rating: 3200 Tags: games, graphs Solve time: 34s Verified: no Solution Working

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 1155B - Game with Telephone Numbers

CF 1155B - Game with Telephone Numbers Rating: 1200 Tags: games, greedy, implementation Solve time: 1m 27s Verified: yes Solution Problem Understanding We are given a digit string of odd length, and two players alternately delete single characters from it. The process continues until only 11 characters remain. At that moment, the remaining subsequence is checked: if it forms a valid “telephone number”, meaning it has length 11 and its...

Codeforces Round 459 (Div. 1)

Codeforces Round 459 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 2/5 | Rating range: 1700-3400 | Time: 25m 47s Problem Name Rating Tags Solve Time Verified A The Monster 1800 dp, greedy, implementation 2m 41s ✓ B MADMAX 1700 dfs-and-similar, dp, games 4m 34s ✗ C Pollywog 2900 combinatorics, dp, matrices 6m 26s ✗ D Stranger Trees 2600 dp, math, matrices 9m 19s ✗ E Upside Down...

CF 1190B - Tokitsukaze, CSL and Stone Game

CF 1190B - Tokitsukaze, CSL and Stone Game Rating: 1800 Tags: games Solve time: 3m 6s Verified: yes Solution Problem Understanding We are given a collection of piles of stones, each pile containing a non-negative integer number of stones. Two players take turns removing exactly one stone from a pile. Tokitsukaze goes first. A player loses if, at the start of their turn, all piles are empty, or if their...

CF 1220C - Substring Game in the Lesson

CF 1220C - Substring Game in the Lesson Rating: 1300 Tags: games, greedy, strings Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given a string s and we need to predict the outcome of a two-player game for each starting position k in the string. The game begins with a substring consisting of a single character at position k . Ann moves first, and each player extends...

CF 1270A - Card Game

CF 1270A - Card Game Rating: 800 Tags: games, greedy, math Solve time: 2m 47s 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...

Codeforces Round 668 (Div. 1)

Codeforces Round 668 (Div. 1) Div. 1 | 5 problems | 2/5 verified | Difficulty 1500-2800 | 20m 9s # Problem Rating Tags Accepted Time ✓ A Balanced Bitstring 1500 implementation, strings 19,385 1m 29s ✓ B Tree Tag 1900 dfs-and-similar, dp, games 8,180 3m 37s ✓ C Fixed Point Removal 2300 binary-search, constructive-algorithms, data-structures 3,048 4m 12s D Game of Pairs 2800 constructive-algorithms, dfs-and-similar, interactive 1,270 4m 8s E...

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 1363C - Game On Leaves

CF 1363C - Game On Leaves Rating: 1600 Tags: games, trees Solve time: 6m 12s Verified: yes Solution Problem Understanding The game is played on a tree, which is an undirected, connected, acyclic graph. Each node is numbered from $1$ to $n$, and one node $x$ is special. Two players take turns removing leaf nodes, where a leaf is a node with only one neighbor, along with its connecting edge....

CF 1365A - Matrix Game

CF 1365A - Matrix Game Rating: 1100 Tags: games, greedy, implementation Solve time: 8m 5s Verified: yes Solution Problem Understanding We are given a grid where some cells are already occupied. Two players alternate turns, and on each move a player must pick a previously unused cell under a strong restriction: no two chosen cells are allowed to share a row or a column. The game ends when a player...

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 646 (Div. 2)

Codeforces Round 646 (Div. 2) Div. 2 | 4 problems | 2/4 verified | Difficulty 1200-2100 | 18m 41s # Problem Rating Tags Accepted Time ✓ A Odd Selection 1200 brute-force, implementation, math 40,389 2m 14s ✓ C Game On Leaves 1600 games, trees 21,072 6m 12s ✓ D Guess The Maximums 2100 binary-search, implementation, interactive 4,413 6m 18s E Tree Shuffling 2000 dfs-and-similar, dp, greedy 7,495 3m 57s

CF 1383B - GameGame

CF 1383B - GameGame Rating: 1900 Tags: bitmasks, constructive algorithms, dp, games, greedy, math Solve time: 1m 32s Verified: yes Solution Problem Understanding The problem describes a two-player game played on an array of non-negative integers. The players take turns removing an element from the array and XOR-ing it with their current score. The game ends when all elements are removed, and the player with the larger score wins, while...

Codeforces Round 666 (Div. 1)

Codeforces Round 666 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 1/5 | Rating range: 1600-3300 | Time: 27m 33s Problem Name Rating Tags Solve Time Verified A Multiples of Length 1600 constructive-algorithms, greedy, number-theory 7m 59s ✗ B Stoned Game 1800 brute-force, constructive-algorithms, games 11m 46s ✓ C Monster Invaders 2300 dp, greedy, implementation 2m 48s ✗ D Rainbow Rectangles 3300 data-structures, sortings, two-pointers 2m 38s ✗...

CF 1396B - Stoned Game

CF 1396B - Stoned Game Rating: 1800 Tags: brute force, constructive algorithms, games, greedy Solve time: 11m 46s Verified: yes Solution The traceback tells us exactly what happened: u, v = map(int, input().split()) ValueError: too many values to unpack (expected 2) The code is trying to read an edge of a tree as two integers u v . But the actual input is: 3 7 4 6 11 11 15...

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 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...

CF 1402C - Star Trek

CF 1402C - Star Trek Rating: 2600 Tags: *special, combinatorics, dfs and similar, dp, games, graphs, matrices, trees Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given a tree of $N$ planets. Each universe contains an identical copy of this tree, so every universe has the same internal structure and the same $N$ nodes connected by $N-1$ undirected edges. There are $D+1$ universes indexed from $0$ to...

CF 1411G - No Game No Life

CF 1411G - No Game No Life Rating: 2700 Tags: bitmasks, games, math, matrices Solve time: 1m 22s Verified: yes Solution Problem Understanding We are asked to calculate the probability that Alice wins a two-player chip-moving game on a directed acyclic graph. Each vertex can hold any number of chips, and players take turns moving a single chip along an outgoing edge. Alice starts first, and the player who cannot...

Codeforces Round 671 (Div. 2)

Codeforces Round 671 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 4/7 | Rating range: 900-2800 | Time: 14m 47s Problem Name Rating Tags Solve Time Verified A Digit Game 900 games, greedy, implementation 1m 13s ✓ B Stairs 1200 brute-force, constructive-algorithms, greedy 1m 37s ✓ C Killjoy 1500 greedy, implementation, math 6m 23s ✗ D1 Sage's Birthday (easy version) 1000 binary-search, constructive-algorithms, greedy 1m 16s ✓ D2...

CF 1419A - Digit Game

CF 1419A - Digit Game Rating: 900 Tags: games, greedy, implementation Solve time: 1m 13s Verified: yes Solution Problem Understanding We are asked to simulate a simple turn-based digit game between two agents, Raze and Breach. Each game starts with a positive integer consisting of $n$ digits. The digits are numbered from left to right, starting with 1. Raze can only mark digits in odd positions, and Breach can only...

2020 ICPC, COMPFEST 12, Indonesia Multi-Provincial Contest (Unrated, Online Mirror, ICPC Rules, Teams Preferred)

2020 ICPC, COMPFEST 12, Indonesia Multi-Provincial Contest (Unrated, Online Mirror, ICPC Rules, Teams Preferred) Type: ICPC/IOI | Problems: 8 | Verified: 3/8 | Rating range: 1300-3100 | Time: 22m 1s Problem Name Rating Tags Solve Time Verified A Arena of Greed 1400 games, greedy 1m 16s ✓ B Blue and Red of Our Faculty! 2600 divide-and-conquer, dp 8m 31s ✗ C Captain of Knights 3100 math 3m 16s ✗ D...

CF 1425A - Arena of Greed

CF 1425A - Arena of Greed Rating: 1400 Tags: games, greedy Solve time: 1m 16s Verified: yes Solution Problem Understanding The problem is a two-player coin game. There is a pile of $N$ gold coins. Players alternate turns, starting with Mr. Chanek. On a turn, a player may either take one coin or, if the pile contains an even number of coins, take exactly half of the pile. Each player...

CF 1427H - Prison Break

CF 1427H - Prison Break Rating: 3500 Tags: binary search, games, geometry, ternary search Solve time: 1m 32s Verified: no Solution Problem Understanding We are asked to compute the minimum speed $v$ at which two guards can prevent a prisoner from escaping a convex polygonal prison. The prisoner starts outside the main perimeter on a fixed point far to the left. He can move freely at speed 1 toward any...

CF 1431G - Number Deletion Game

CF 1431G - Number Deletion Game Rating: 2100 Tags: *special, dp, games, greedy Solve time: 1m 23s Verified: yes Solution Problem Understanding We are given a collection of distinct integers. The game is played in a sequence of rounds, and each round removes two numbers and converts their difference into score. The interaction between players is asymmetric: Alice picks first, but she is restricted from taking the current maximum element,...

CF 1434E - A Convex Game

CF 1434E - A Convex Game Rating: 3500 Tags: dsu, games Solve time: 1m 8s Verified: yes Solution Problem Understanding We are given several independent games. Each game consists of a strictly increasing array of integers. Two players alternate moves, and on each move a player selects one element from the array. The chosen indices must form a strictly increasing sequence over time, so once you pick a position, you...

Codeforces Round 679 (Div. 1, based on Technocup 2021 Elimination Round 1)

Codeforces Round 679 (Div. 1, based on Technocup 2021 Elimination Round 1) Type: Div. 1 | Problems: 1 | Verified: 1/1 | Rating range: 3500-3500 | Time: 1m 8s Problem Name Rating Tags Solve Time Verified E A Convex Game 3500 dsu, games 1m 8s ✓

CF 1439E - Cheat and Win

CF 1439E - Cheat and Win Rating: 3500 Tags: bitmasks, data structures, games, trees Solve time: 1m 49s Verified: no Solution Problem Understanding The game is played on a very large grid, but only a very special subset of cells is relevant. A cell $(x, y)$ is considered valid only when the bitwise condition $x & y = 0$ holds. If we connect every valid cell to its four side-adjacent...

CF 1442F - Differentiating Games

CF 1442F - Differentiating Games Rating: 3400 Tags: games, interactive Solve time: 1m 21s Verified: no Solution Problem Understanding We are dealing with an interactive combinatorial game on a directed graph. Each vertex may hold a token, and two players alternate moves. On a turn, a player chooses any token and moves it along an outgoing edge. If a player cannot move any token, they lose. The interactor selects a...

CF 1451F - Nullify The Matrix

CF 1451F - Nullify The Matrix Rating: 2700 Tags: constructive algorithms, games Solve time: 4m 26s Verified: yes Solution Problem Understanding The problem describes a two-player game played on an $n \times m$ matrix of non-negative integers. Players alternate moves, starting with Ashish. On each move, a player selects a starting cell with a non-zero value, chooses an ending cell that is not above or to the left of the...

CF 1451D - Circle Game

CF 1451D - Circle Game Rating: 1700 Tags: games, geometry, math Solve time: 1m 5s Verified: yes Solution Problem Understanding We are given a circle centered at the origin with radius $d$. Inside this circle lie all integer lattice points $(x, y)$ such that $x^2 + y^2 \le d^2$, but we only care about points in the first quadrant including axes, so $x \ge 0, y \ge 0$. Two players...

Educational Codeforces Round 99 (Rated for Div. 2)

Educational Codeforces Round 99 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 0/7 | Rating range: 800-2900 | Time: 18m 2s Problem Name Rating Tags Solve Time Verified A Strange Functions 800 math, number-theory 2m 34s ✗ B Jumps 1200 constructive-algorithms, math 1m 32s ✗ C Ping-pong 1100 constructive-algorithms, games, math 1m 57s ✗ D Sequence and Swaps 1600 dp, greedy, sortings 6m 35s ✗ E...

CF 1455C - Ping-pong

CF 1455C - Ping-pong Rating: 1100 Tags: constructive algorithms, games, math Solve time: 1m 57s Verified: no Solution Problem Understanding We are simulating a ping-pong game where two players, Alice and Bob, have finite stamina. Each action, whether serving or returning, costs 1 stamina. Alice always serves first. The game progresses in "plays," which are single rallies that continue until one player fails to hit the ball back. The winner...

CF 1458E - Nim Shortcuts

CF 1458E - Nim Shortcuts Rating: 3100 Tags: data structures, games Solve time: 1m 49s Verified: no Solution Problem Understanding We are asked to analyze a variation of the two-heap Nim game. In classic Nim with two heaps, each player can take any positive number of stones from either heap. The player who cannot make a move loses. The twist here is the presence of "shortcut positions," which are specific...

Good Bye 2019

Good Bye 2019 Special | 9 problems | 2/9 verified | Difficulty 800-3500 | 55m 51s # Problem Rating Tags Accepted Time ✓ A Card Game 800 games, greedy, math 17,812 2m 47s B Interesting Subarray 1200 constructive-algorithms, greedy, math 17,372 10m 31s C Make Good 1400 bitmasks, constructive-algorithms, math 15,038 5m 12s D Strange Device 1900 constructive-algorithms, interactive, math 4,868 2m 34s ✓ E Divide Points 2300 constructive-algorithms, geometry,...

Codeforces Round 693 (Div. 3)

Codeforces Round 693 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 3/7 | Rating range: 800-2100 | Time: 28m 54s Problem Name Rating Tags Solve Time Verified A Cards for Friends 800 greedy, math 1m 37s ✓ B Fair Division 800 dp, greedy, math 5m 25s ✓ C Long Jumps 1100 dp, graphs 2m 53s ✗ D Even-Odd Game 1200 dp, games, greedy 1m 53s ✓ E Correct...

CF 1472D - Even-Odd Game

CF 1472D - Even-Odd Game Rating: 1200 Tags: dp, games, greedy, sortings Solve time: 1m 53s Verified: yes Solution Problem Understanding We are given an array of integers, and two players alternately remove elements from it. Alice starts first. Every time a player removes a number, only certain values actually contribute to their score: Alice gains points only from even numbers she picks, while Bob gains points only from odd...

Codeforces Round 700 (Div. 2)

Codeforces Round 700 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-900 | Time: 5m 1s Problem Name Rating Tags Solve Time Verified A Yet Another String Game 800 games, greedy, strings 3m 3s ✗ B The Great Hero 900 greedy, implementation, sortings 1m 58s ✓

CF 1480A - Yet Another String Game

CF 1480A - Yet Another String Game Rating: 800 Tags: games, greedy, strings Solve time: 3m 3s Verified: no Solution I can't reliably diagnose this one from the sample alone because the sample input/output pair does not identify the problem. The behavior strongly suggests that the Python program being tested is actually a solution for a completely different problem: Your input contains 3 test cases. The expected output is three...

Codeforces Round 706 (Div. 1)

Codeforces Round 706 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 0/6 | Rating range: 1200-3300 | Time: 24m 23s Problem Name Rating Tags Solve Time Verified A Diamond Miner 1200 geometry, greedy, math 6m 5s ✗ B Let's Go Hiking 1900 games, greedy 3m 32s ✗ C Garden of the Sun 2300 constructive-algorithms, graphs 5m 29s ✗ D BFS Trees 2600 combinatorics, dfs-and-similar, graphs 1m 16s ✗...

CF 1495B - Let's Go Hiking

CF 1495B - Let's Go Hiking Rating: 1900 Tags: games, greedy Solve time: 3m 32s Verified: no Solution Problem Understanding We are given a permutation laid out on a line of positions. Two players control two markers, one starting from an index chosen by Qingshan and the other chosen by Daniel after seeing the first choice. They then take turns moving these markers along adjacent positions, but each move is...

CF 1498F - Christmas Game

CF 1498F - Christmas Game Rating: 2500 Tags: bitmasks, data structures, dfs and similar, dp, games, math, trees Solve time: 5m 30s Verified: no Solution Problem Understanding We are asked to analyze a two-player game on a tree. Each node of the tree contains a certain number of presents, and players take turns moving presents from nodes to their $k$-th ancestor. The player who cannot make a move loses. The...

Codeforces Round 712 (Div. 1)

Codeforces Round 712 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 1/6 | Rating range: 1600-3500 | Time: 26m 57s Problem Name Rating Tags Solve Time Verified A Balance the Bits 1600 constructive-algorithms, greedy 3m 28s ✗ B 3-Coloring 1700 constructive-algorithms, games, interactive 6m 29s ✗ C Travelling Salesman Problem 2200 binary-search, data-structures, dp 11m 59s ✓ D Flip the Cards 2600 2-sat, constructive-algorithms, data-structures 1m 1s ✗...

CF 1503B - 3-Coloring

CF 1503B - 3-Coloring Rating: 1700 Tags: constructive algorithms, games, interactive Solve time: 6m 29s Verified: no Solution Problem Understanding Alice and Bob are filling an $n \times n$ grid. On every turn Alice first announces a color from ${1,2,3}$. Bob must then choose an empty cell and place a token of a different color. Bob loses immediately if two edge-adjacent cells ever end up with the same color. His...

CF 1511G - Chips on a Board

CF 1511G - Chips on a Board Rating: 2700 Tags: bitmasks, brute force, data structures, dp, games, two pointers Solve time: 2m 41s Verified: yes Solution Problem Understanding We are given a rectangular board with n rows and m columns. Each row contains exactly one chip. The chips can be located in any column of their respective row. Alice and Bob play a restricted version of a Nim game: first,...

Codeforces Round 721 (Div. 2)

Codeforces Round 721 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2500 | Time: 15m 3s Problem Name Rating Tags Solve Time Verified A And Then There Were K 800 bitmasks 2m 39s ✗ B1 Palindrome Game (easy version) 1200 constructive-algorithms, games 2m 2s ✓ B2 Palindrome Game (hard version) 1900 constructive-algorithms, games 2m 14s ✓ C Sequence Pair Weight 1600 hashing, implementation, math...

CF 1527B2 - Palindrome Game (hard version)

CF 1527B2 - Palindrome Game (hard version) Rating: 1900 Tags: constructive algorithms, games Solve time: 2m 14s Verified: yes Solution Problem Understanding We are given a binary string and two players, Alice and Bob, who alternately modify it. A move can either change a single '0' into '1' at a cost of one dollar, or reverse the entire string for free. Reversal is only available when the current string is...

CF 1527B1 - Palindrome Game (easy version)

CF 1527B1 - Palindrome Game (easy version) Rating: 1200 Tags: constructive algorithms, games Solve time: 2m 2s Verified: yes Solution Problem Understanding We are given a binary string that is already symmetric from both ends. The game starts with Alice and Bob alternating turns, and the only thing that matters financially is how many times each player is forced to flip a character from 0 to 1 , since each...

CF 1536F - Omkar and Akmar

CF 1536F - Omkar and Akmar Rating: 2600 Tags: chinese remainder theorem, combinatorics, constructive algorithms, fft, games, geometry, math, meet-in-the-middle, string suffix structures Solve time: 2m 23s Verified: yes Solution Problem Understanding We are asked to count all possible distinct games played on a circular board with $n$ cells, where two players take turns placing letters A or B . Akmar moves first. A letter cannot be placed adjacent to...

Codeforces Round 726 (Div. 2)

Codeforces Round 726 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 3/7 | Rating range: 800-2200 | Time: 50m 44s Problem Name Rating Tags Solve Time Verified A Arithmetic Array 800 greedy, math 2m 26s ✓ B Bad Boy 900 constructive-algorithms, greedy, math 22m 55s ✗ C Challenging Cliffs 1200 constructive-algorithms, greedy, implementation 8m 10s ✗ D Deleting Divisors 1700 games, math, number-theory 2m 30s ✗ E1 Erase...

CF 1537D - Deleting Divisors

CF 1537D - Deleting Divisors Rating: 1700 Tags: games, math, number theory Solve time: 2m 30s Verified: no Solution Problem Understanding We start with a positive integer $n$. Two players alternate turns, with Alice moving first. On each turn, the current player chooses a proper divisor of the current number, meaning a divisor that is neither $1$ nor the number itself, and subtracts it from the number. The game continues...

CF 1584E - Game with Stones

CF 1584E - Game with Stones Rating: 2300 Tags: binary search, data structures, games, greedy Solve time: 2m 39s Verified: yes Solution Problem Understanding We are given a sequence of piles of stones, each with a non-negative integer count. Bob can repeatedly remove one stone from two adjacent piles. If a pile becomes empty, it no longer counts as part of any adjacent pair. A sequence of piles is called...

CF 1585G - Poachers

CF 1585G - Poachers Rating: 2500 Tags: dp, games, graphs, trees Solve time: 44s Verified: no Solution I can't fit the complete editorial you requested within a single response without either truncating sections or sacrificing the level of detail you asked for. Your requested structure includes seven substantial sections, full correctness reasoning, a complete implementation, multiple worked traces, and assert-based tests, which together exceed the response length available. I can,...

CF 1605D - Treelabeling

CF 1605D - Treelabeling Rating: 2100 Tags: bitmasks, constructive algorithms, dfs and similar, games, greedy, implementation, trees Solve time: 1m 47s Verified: no Solution Problem Understanding We are asked to relabel the nodes of a tree so that the first player, Eikooc, can maximize her number of guaranteed winning starting positions. The game itself is a token-moving game on a tree where players alternate moving the token to an unvisited...

CF 1610I - Mashtali vs AtCoder

CF 1610I - Mashtali vs AtCoder Rating: 3100 Tags: games, trees Solve time: 2m Verified: no Solution Problem Understanding We are given a tree of $n$ vertices. The game is played on the tree by two players who take turns deleting edges. After an edge is removed, any connected component that contains no “pinned” vertex is completely discarded. The first player who cannot make a move loses. The twist is...

CF 1615E - Purple Crayon

CF 1615E - Purple Crayon Rating: 2400 Tags: data structures, dfs and similar, games, graphs, greedy, math, sortings, trees Solve time: 1m 41s Verified: no Solution Problem Understanding We are given a rooted tree with $n$ nodes, rooted at node 1, where all nodes start white. Two players, Red and Blue, take turns coloring nodes. Red goes first and can color at most $k$ nodes red by choosing entire subtrees....

CF 1617E - Christmas Chocolates

CF 1617E - Christmas Chocolates Rating: 2700 Tags: dfs and similar, dp, games, graphs, implementation, math, number theory, shortest paths, trees Solve time: 1m 54s Verified: no Solution Problem Understanding We are given a box of chocolates, each with a distinct type represented by a non-negative integer. Icy wants to make at least one pair of chocolates have the same type, but before any exchanges, she chooses two chocolates, say...

Codeforces Round 766 (Div. 2)

Codeforces Round 766 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 4/6 | Rating range: 800-2700 | Time: 13m 39s Problem Name Rating Tags Solve Time Verified A Not Shading 800 constructive-algorithms, implementation 1m 35s ✓ B Not Sitting 1300 games, greedy, sortings 1m 32s ✓ C Not Assigning 1400 constructive-algorithms, dfs-and-similar, number-theory 1m 37s ✓ D Not Adding 1900 brute-force, dp, math 1m 20s ✓ E Not...

CF 1627B - Not Sitting

CF 1627B - Not Sitting Rating: 1300 Tags: games, greedy, sortings Solve time: 1m 32s Verified: yes Solution Problem Understanding We are given a classroom represented as a grid with $n$ rows and $m$ columns. Each cell is a seat. Tina can paint exactly $k$ seats pink, where $k$ ranges from 0 to $n \cdot m - 1$. Rahul then chooses a seat avoiding painted seats, aiming to sit as...

CF 1628D1 - Game on Sum (Easy Version)

CF 1628D1 - Game on Sum (Easy Version) Rating: 2100 Tags: combinatorics, dp, games, math Solve time: 2m 18s Verified: no Solution Problem Understanding We are asked to analyze a two-player game between Alice and Bob. The game lasts for n turns, and in each turn Alice chooses a number between 0 and k . Bob then decides whether to add or subtract that number from the running total score,...

CF 1628D2 - Game on Sum (Hard Version)

CF 1628D2 - Game on Sum (Hard Version) Rating: 2400 Tags: combinatorics, dp, games, math Solve time: 1m 33s Verified: no Solution Problem Understanding Alice and Bob play a game of alternating choices over n turns. On each turn, Alice picks a number between 0 and k . Bob then decides whether to add or subtract that number from the total score, with the constraint that he must add at...

CF 1659F - Tree and Permutation Game

CF 1659F - Tree and Permutation Game Rating: 3000 Tags: dfs and similar, games, graphs, trees Solve time: 2m 6s Verified: yes Solution Problem Understanding We are given a tree where every vertex hosts a position in a permutation. Separately, there is a token sitting on one vertex. The game evolves in alternating moves between Alice and Bob. Alice’s move does not change the tree. Instead, she manipulates the permutation...

CF 1665D - GCD Guess

CF 1665D - GCD Guess Rating: 2000 Tags: bitmasks, chinese remainder theorem, constructive algorithms, games, interactive, math, number theory Solve time: 1m 46s Verified: no Solution Problem Understanding We are asked to find a hidden positive integer $x$ between 1 and $10^9$. Instead of observing $x$ directly, we can query the greatest common divisor of two numbers shifted by $x$. Specifically, for any two positive integers $a$ and $b$, the...

Codeforces Global Round 20

Codeforces Global Round 20 Type: Global | Problems: 10 | Verified: 4/10 | Rating range: 800-3200 | Time: 21m 54s Problem Name Rating Tags Solve Time Verified A Log Chopping 800 games, implementation, math 1m 28s ✓ B I love AAAB 800 constructive-algorithms, implementation 6m 46s ✗ C Unequal Array 1100 constructive-algorithms, greedy, implementation 1m 26s ✓ D Cyclic Rotation 1700 constructive-algorithms, greedy, implementation 1m 57s ✗ E notepad.exe 2200...

CF 1672A - Log Chopping

CF 1672A - Log Chopping Rating: 800 Tags: games, implementation, math Solve time: 1m 28s Verified: yes Solution Problem Understanding We are asked to determine the winner in a simple two-player game with logs of integer lengths. There are $n$ logs, and two players take turns splitting a single log into two positive integer pieces. The first player unable to make a move loses. Each test case provides the number...

Codeforces Round 785 (Div. 2)

Codeforces Round 785 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 1/6 | Rating range: 800-2500 | Time: 17m 48s Problem Name Rating Tags Solve Time Verified A Subtle Substring Subtraction 800 games, greedy, strings 1m 51s ✓ B A Perfectly Balanced String? 1100 brute-force, greedy, strings 2m 4s ✗ C Palindrome Basis 1500 brute-force, dp, math 7m 36s ✗ D Lost Arithmetic Progression 1900 combinatorics, math, number-theory...

CF 1673A - Subtle Substring Subtraction

CF 1673A - Subtle Substring Subtraction Rating: 800 Tags: games, greedy, strings Solve time: 1m 51s Verified: yes Solution Problem Understanding We are given several independent rounds. In each round, Alice and Bob repeatedly delete contiguous parts of a string until nothing remains. The deleted characters contribute to their personal scores, where each letter has a fixed value from 1 for a up to 26 for z . The twist...

Educational Codeforces Round 129 (Rated for Div. 2)

Educational Codeforces Round 129 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2600 | Time: 19m 35s Problem Name Rating Tags Solve Time Verified A Game with Cards 800 games, greedy 10m 58s ✗ B Card Trick 800 implementation, math 1m 37s ✓ C Double Sort 1200 implementation, sortings 2m 5s ✗ D Required Length 1700 brute-force, dfs-and-similar, dp 1m 25s ✓...

CF 1681A - Game with Cards

CF 1681A - Game with Cards Rating: 800 Tags: games, greedy Solve time: 10m 58s Verified: no Solution Problem Understanding Two players each hold a multiset of integers. They play a turn-based game where the only rule is that every newly played number must be strictly larger than the previous one. Players alternate turns, and on each turn a player must pick a remaining card that is larger than the...

CF 1684A - Digit Minimization

CF 1684A - Digit Minimization Rating: 800 Tags: constructive algorithms, games, math, strings Solve time: 1m 57s Verified: yes Solution Problem Understanding We are given an integer with no zero digits, and two players, Alice and Bob, play a turn-based game on its digits. Alice always moves first and can swap any two digits at different positions. Bob always removes the last digit of the number. The game ends when...

Codeforces Round 801 (Div. 2) and EPIC Institute of Technology Round

Codeforces Round 801 (Div. 2) and EPIC Institute of Technology Round Type: Div. 2 | Problems: 6 | Verified: 4/6 | Rating range: 800-2700 | Time: 13m 10s Problem Name Rating Tags Solve Time Verified A Subrectangle Guess 800 games 2m 22s ✓ B Circle Game 1000 games, greedy 2m 6s ✓ C Zero Path 1700 brute-force, data-structures, dp 3m 1s ✗ D1 Tree Queries (Easy Version) 2200 brute-force, constructive-algorithms,...

CF 1695A - Subrectangle Guess

CF 1695A - Subrectangle Guess Rating: 800 Tags: games Solve time: 2m 22s Verified: yes Solution Problem Understanding We are given a grid containing distinct integers. Michael chooses dimensions h × w , then Joe secretly selects any subrectangle of exactly that size. Michael must name the maximum value inside Joe's chosen rectangle before seeing which rectangle was selected. Since all values are distinct, the entire board has a unique...

CF 1695B - Circle Game

CF 1695B - Circle Game Rating: 1000 Tags: games, greedy Solve time: 2m 6s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game played on a circle of stone piles. Each pile has a certain number of stones. Players take turns removing a positive number of stones from the current pile. The turns move clockwise, so after a player removes stones from pile i , the...

CF 1704F - Colouring Game

CF 1704F - Colouring Game Rating: 2600 Tags: constructive algorithms, dp, games Solve time: 2m 40s Verified: no Solution Problem Understanding We are given a row of cells, each painted either red or blue. Alice and Bob take turns, starting with Alice. On her turn, Alice selects any two neighboring cells such that at least one of them is red and paints them both white. Bob does the same on...

CF 1710E - Two Arrays

CF 1710E - Two Arrays Rating: 2400 Tags: binary search, games, graph matchings Solve time: 1m 55s Verified: yes Solution Problem Understanding The game takes place on a conceptual grid where each position is identified by a row index and a column index. Each row has a fixed value from array a , and each column has a fixed value from array b . If the game ends at a...

CF 1719A - Chip Game

CF 1719A - Chip Game Rating: 800 Tags: games, math Solve time: 1m 39s Verified: yes Solution Problem Understanding We have an $n \times m$ board and a chip that starts in the lower-left corner. On each turn, a player chooses exactly one direction, either up or right, and moves the chip by any odd number of cells in that direction. The chip cannot leave the board. The game ends...

CF 1737C - Ela and Crickets

CF 1737C - Ela and Crickets Rating: 1500 Tags: constructive algorithms, games, implementation, math Solve time: 2m 28s Verified: yes Solution Problem Understanding We are given an n x n chessboard with exactly three white crickets arranged in an "L" shape. Each cricket moves like a jumper: it can leap over an adjacent cricket in any of the eight directions (horizontal, vertical, diagonal) but cannot move unless there is a...

CF 1738C - Even Number Addicts

CF 1738C - Even Number Addicts Rating: 1500 Tags: dp, games, greedy, math Solve time: 6m 50s Verified: no Solution Diagnosis The failure is not in I/O or iteration mechanics, but in the logic of what an “isolated cell” actually means. The previous solution implicitly assumed a global classification based only on board dimensions, and then defaulted to returning $(1,1)$ for all cases. That contradicts the actual definition: isolation is...

CF 1739C - Card Game

CF 1739C - Card Game Rating: 1500 Tags: combinatorics, constructive algorithms, dp, games Solve time: 2m 17s Verified: no Solution Problem Understanding We are given a complete set of distinct cards labeled from 1 to n, where n is even. Each card is assigned to exactly one of two players, Alex and Boris, so each player ends up with n/2 cards. Once the split is fixed, they play a deterministic...

Codeforces Round 832 (Div. 2)

Codeforces Round 832 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 2/5 | Rating range: 800-2900 | Time: 20m 27s Problem Name Rating Tags Solve Time Verified A Two Groups 800 constructive-algorithms, greedy 6m 6s ✓ B BAN BAN 900 constructive-algorithms 2m 39s ✗ C Swap Game 1200 games 2m 12s ✓ D Yet Another Problem 1900 binary-search, bitmasks, constructive-algorithms 2m 12s ✗ E List Generation 2900 combinatorics,...

CF 1747C - Swap Game

CF 1747C - Swap Game Rating: 1200 Tags: games Solve time: 2m 12s Verified: yes Solution Problem Understanding We are asked to determine the winner in a two-player game played on an array of positive integers. Alice moves first. On each turn, the player inspects the first element of the array. If it is zero, the player loses immediately. Otherwise, the player chooses a position in the array from the...

Educational Codeforces Round 138 (Rated for Div. 2)

Educational Codeforces Round 138 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 2/6 | Rating range: 800-2800 | Time: 24m 42s Problem Name Rating Tags Solve Time Verified A Cowardly Rooks 800 greedy, implementation 5m 44s ✗ B Death's Blessing 900 greedy 2m 33s ✗ C Number Game 1400 binary-search, data-structures, games 2m 10s ✗ D Counting Arrays 1900 combinatorics, dp, math 2m 47s ✓ E...

CF 1749C - Number Game

CF 1749C - Number Game Rating: 1400 Tags: binary search, data structures, games, greedy, implementation Solve time: 2m 10s Verified: no Solution Problem Understanding We are asked to analyze a two-player game played on an array of positive integers. Alice chooses a number of stages $k$ she wants to play, and in each stage she must remove an element from the array that is at most the number of the...

CF 1770D - Koxia and Game

CF 1770D - Koxia and Game Rating: 2000 Tags: constructive algorithms, data structures, dfs and similar, dsu, flows, games, graph matchings, graphs, implementation Solve time: 1m 51s Verified: no Solution Problem Understanding We are given two arrays, a and b , each of length n , with elements between 1 and n . We have to choose a third array c of the same length so that a constructed game...

Codeforces Round 839 (Div. 3)

Codeforces Round 839 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 1/7 | Rating range: 800-2200 | Time: 14m 59s Problem Name Rating Tags Solve Time Verified A A+B? 800 implementation 2m 29s ✗ B Matrix Rotation 800 brute-force, implementation 1m 12s ✗ C Different Differences 1000 constructive-algorithms, greedy, math 3m 21s ✗ D Absolute Sorting 1400 constructive-algorithms, math 3m 22s ✗ E Permutation Game 1700 games 2m...

CF 1772E - Permutation Game

CF 1772E - Permutation Game Rating: 1700 Tags: games Solve time: 2m 27s Verified: no Solution Problem-Type Check This is a Type B (prove inequality) problem, not Type C. The task is to prove that $$\frac1{a^3(b+c)}+\frac1{b^3(c+a)}+\frac1{c^3(a+b)}\ge \frac32$$ for all positive $a,b,c$ satisfying $abc=1$. A valid solution must establish the inequality for all admissible triples and correctly identify any equality case if it arises from the argument. Step-by-Step Verification Step 1:...

SWERC 2022-2023 - Online Mirror (Unrated, ICPC Rules, Teams Preferred)

SWERC 2022-2023 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) Type: ICPC/IOI | Problems: 14 | Verified: 4/14 | Rating range: 800-3500 | Time: 26m 25s Problem Name Rating Tags Solve Time Verified A Walking Boy 800 greedy 1m 17s ✓ B Vittorio Plays with LEGO Bricks 2200 dp, geometry 1m 38s ✗ C Library game 2500 games, greedy, interactive 1m 21s ✗ D Teamwork 2800 constructive-algorithms, greedy, math 1m...

CF 1776I - Spinach Pizza

CF 1776I - Spinach Pizza Rating: 2500 Tags: games, geometry, greedy, interactive Solve time: 1m 19s Verified: no Solution Problem Understanding We are given a strictly convex polygon with labeled vertices in counterclockwise order. Each move consists of choosing one currently unused vertex. The chosen vertex determines a triangle formed by that vertex and its two adjacent vertices in the current polygon, and that triangle is removed from the remaining...

CF 1776C - Library game

CF 1776C - Library game Rating: 2500 Tags: games, greedy, interactive, sortings Solve time: 1m 21s Verified: no Solution Problem Understanding We are playing a sequential game on a line of labeled sections, each section representing a distinct subject. Each day, one of two players chooses a contiguous interval of sections, constrained by a fixed length coming from a multiset of available “passes”. After the interval is announced, the opponent...

CF 1784E - Infinite Game

CF 1784E - Infinite Game Rating: 3100 Tags: brute force, combinatorics, dp, games, probabilities Solve time: 2m 10s Verified: yes Solution Problem Understanding We are given a short string consisting of characters that can be interpreted as decisions in a repeated competitive process. Each character represents a round outcome between two players, and the string is repeated infinitely to generate an endless sequence of rounds. These rounds are grouped into...

CF 1796E - Colored Subgraphs

CF 1796E - Colored Subgraphs Rating: 2500 Tags: dfs and similar, dp, games, greedy, trees Solve time: 1m 49s Verified: no Solution Problem Understanding We are given a tree with $n$ vertices, and we are allowed to choose any vertex $r$ as a root. Once the root is fixed, every vertex gets a distance label $d_v$, which is simply how far it is from $r$. After this, we assign colors...

CF 1817D - Toy Machine

CF 1817D - Toy Machine Rating: 2700 Tags: constructive algorithms, games, implementation Solve time: 1m 9s Verified: yes Solution Problem Understanding We are given a two-row toy machine with an odd number $n$ of cells in each row. The top row initially holds $n-2$ toys, placed in all cells except the two corners. The bottom row is mostly empty, with the exception that its leftmost, rightmost, and central cells are...

CF 1823E - Removing Graph

CF 1823E - Removing Graph Rating: 2500 Tags: brute force, dp, games, graphs, math Solve time: 1m 13s Verified: yes Solution Problem Understanding We are asked to determine the winner in a two-player game played on a special type of graph. The graph has each vertex of degree exactly 2, which immediately tells us that every connected component is either a cycle or a simple loop. There are no self-loops...

Codeforces Round 879 (Div. 2)

Codeforces Round 879 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 2/6 | Rating range: 800-2500 | Time: 9m 54s Problem Name Rating Tags Solve Time Verified A Unit Array 800 greedy, math 1m 53s ✗ B Maximum Strength 1000 greedy, math 1m 38s ✓ C Game with Reversing 1200 games, greedy, math 1m 43s ✗ D Survey in Class 1900 brute-force, data-structures, greedy 1m 52s ✗ E...

CF 1834C - Game with Reversing

CF 1834C - Game with Reversing Rating: 1200 Tags: games, greedy, math, strings Solve time: 1m 43s Verified: no Solution Problem Understanding We are given two strings of equal length. In a turn-based game, Alice can modify any single character in either string, while Bob can take an entire string and reverse it. The game stops immediately when the two strings become identical, and the total number of moves taken...

Educational Codeforces Round 150 (Rated for Div. 2)

Educational Codeforces Round 150 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2700 | Time: 11m 57s Problem Name Rating Tags Solve Time Verified A Game with Board 800 constructive-algorithms, games 1m 4s ✓ B Keep it Beautiful 1000 implementation 1m 46s ✓ C Ranom Numbers 1800 brute-force, dp, greedy 4m 37s ✗ D Pairs of Segments 2000 data-structures, greedy, sortings 1m...

CF 1841A - Game with Board

CF 1841A - Game with Board Rating: 800 Tags: constructive algorithms, games Solve time: 1m 4s Verified: yes Solution Problem Understanding We start with a multiset of numbers where all values are identical and equal to one, and the size of this multiset is given by $n$. Two players alternate turns, with Alice moving first. A move consists of selecting at least two equal numbers currently present, removing them, and...

CodeTON Round 5 (Div. 1 + Div. 2, Rated, Prizes!)

CodeTON Round 5 (Div. 1 + Div. 2, Rated, Prizes!) Type: Div. 1+2 | Problems: 9 | Verified: 3/9 | Rating range: 800-3500 | Time: 16m 2s Problem Name Rating Tags Solve Time Verified A Tenzing and Tsondu 800 games, math 58s ✗ B Tenzing and Books 1100 bitmasks, greedy, math 1m 45s ✓ C Tenzing and Balls 1500 dp 3m 10s ✗ D Tenzing and His Animal Friends 1900...

CF 1842A - Tenzing and Tsondu

CF 1842A - Tenzing and Tsondu Rating: 800 Tags: games, math Solve time: 58s Verified: no Solution Correctness The proposed “solution” does not address the mathematical exercise at all. Instead, it discusses a Python runtime error and competitive programming implementation details unrelated to Exercise 3.3.1.15, which asks for the Jacobian determinant of an $n$-dimensional polar (spherical) coordinate transformation. There is no derivation, computation, or proof presented for the formula $$dx_1,dx_2\cdots...

Codeforces Round 884 (Div. 1 + Div. 2)

Codeforces Round 884 (Div. 1 + Div. 2) Type: Div. 1+2 | Problems: 9 | Verified: 1/9 | Rating range: 800-3400 | Time: 17m 33s Problem Name Rating Tags Solve Time Verified A Subtraction Game 800 constructive-algorithms, games 1m 46s ✗ B Permutations & Primes 1000 constructive-algorithms, math 1m 21s ✗ C Particles 1300 dp, greedy, implementation 5m 10s ✗ D Row Major 1400 constructive-algorithms, greedy, math 1m 44s ✓...

CF 1844A - Subtraction Game

CF 1844A - Subtraction Game Rating: 800 Tags: constructive algorithms, games Solve time: 1m 46s Verified: no Solution Problem Understanding We are given two move sizes, $a$ and $b$, with $a < b$. Two players play a subtraction game starting from a pile of $n$ stones. On each turn, a player must remove exactly $a$ or exactly $b$ stones. A player who cannot make a valid move loses immediately. The...

Codeforces Round 885 (Div. 2)

Codeforces Round 885 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 2/6 | Rating range: 900-2600 | Time: 12m 17s Problem Name Rating Tags Solve Time Verified A Vika and Her Friends 900 games, math 1m 31s ✗ B Vika and the Bridge 1200 binary-search, data-structures, greedy 5m 10s ✗ C Vika and Price Tags 1800 math, number-theory 1m 47s ✗ D Vika and Bonuses 2200 binary-search, brute-force,...

CF 1848A - Vika and Her Friends

CF 1848A - Vika and Her Friends Rating: 900 Tags: games, math Solve time: 1m 31s Verified: no Solution Problem Understanding We are asked to model a pursuit scenario on a rectangular grid representing a mall. Vika starts in a specific room, and her friends start in other rooms. Every minute, Vika moves first to an adjacent room (up, down, left, right), then each friend observes her new position and...

CF 2197C - Game with a Fraction

CF 2197C - Game with a Fraction Rating: 1200 Tags: games, greedy, math Solve time: 2m 10s Verified: no Solution The value $V = 7\frac{1}{16}$ corresponds to the chi-square statistic computed from $k = 11$ categories, as in Eq. (5). The number of degrees of freedom is therefore $\nu = k - 1 = 10$. To determine whether $V$ is improbably high, one consults the line of Table 1 corresponding...

CF 2191C - Sorting Game

CF 2191C - Sorting Game Rating: 1200 Tags: games Solve time: 3m 14s Verified: no Solution Problem Understanding We are given a weighted undirected graph. We must choose exactly $n-1$ edges. If those $n-1$ edges form a spanning tree, the choice is forbidden. We want the minimum possible total weight among all choices of $n-1$ edges that do not form a tree. A graph on $n$ vertices with exactly $n-1$...

CF 2191D2 - Sub-RBS (Hard Version)

CF 2191D2 - Sub-RBS (Hard Version) Rating: 1900 Tags: dp, games Solve time: 1m 24s Verified: no Solution Problem Understanding We are given a string s of parentheses of length n . The task is to consider all non-empty subsequences of s and compute a "score" for each. The score is defined as follows: if the subsequence is not a regular bracket sequence, its score is 0. If it is...

CF 2188E - Jerry and Tom

CF 2188E - Jerry and Tom Rating: 2300 Tags: data structures, dfs and similar, games, graphs, greedy, trees Solve time: 2m 3s Verified: yes Solution Problem Understanding Every vertex has an edge to the next vertex, and possibly one additional long jump to a larger vertex. The extra edges never cross. If we draw every edge above the number line, no two extra edges form the pattern $u_i < u_j...

CF 2151E - Limited Edition Shop

CF 2151E - Limited Edition Shop Rating: 2100 Tags: data structures, dp, games, greedy Solve time: 1m 26s Verified: no Solution Problem Understanding We are asked to simulate a limited-edition shop where Alice and Bob take turns picking items, but with a twist: we do not control who goes first or in which order they enter. Each item has a value according to us, and Alice and Bob each have...

Codeforces Round 1028 (Div. 2)

Codeforces Round 1028 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 1/6 | Rating range: 800-2900 | Time: 13m 21s Problem Name Rating Tags Solve Time Verified A Gellyfish and Tricolor Pansy 800 games, greedy 1m 56s ✗ B Gellyfish and Baby's Breath 1300 greedy, math, sortings 2m 45s ✗ C Gellyfish and Flaming Peony 1500 brute-force, dfs-and-similar, dp 2m 3s ✓ D Gellyfish and Camellia Japonica 2100...

CF 2116A - Gellyfish and Tricolor Pansy

CF 2116A - Gellyfish and Tricolor Pansy Rating: 800 Tags: games, greedy Solve time: 1m 56s Verified: no Solution Problem Understanding We are asked to predict the winner of a turn-based duel between two players, Gellyfish and Flower. Each player has a main character and a knight, each with its own health points (HP). Gellyfish has a HP, Flower has b HP, Gellyfish's knight has c HP, and Flower's knight...

CF 2007D - Iris and Game on the Tree

CF 2007D - Iris and Game on the Tree Rating: 1700 Tags: games, graphs, greedy, trees Solve time: 5m 47s Verified: no Solution Problem Understanding We are given a tree rooted at vertex 1 where each node contains either a 0, 1, or an undecided value represented as ? . Each leaf has a "weight," defined by walking from the root to that leaf, counting the number of 10 substrings...

Educational Codeforces Round 169 (Rated for Div. 2)

Educational Codeforces Round 169 (Rated for Div. 2) Type: Div. 2 | Problems: 7 | Verified: 3/7 | Rating range: 800-3200 | Time: 18m 35s Problem Name Rating Tags Solve Time Verified A Closest Point 800 implementation, math 1m 10s ✓ B Game with Doors 1000 brute-force, greedy 5m 23s ✗ C Splitting Items 1100 games, greedy, sortings 6m 31s ✗ D Colored Portals 1600 binary-search, brute-force, data-structures 1m 42s...

CF 2004C - Splitting Items

CF 2004C - Splitting Items Rating: 1100 Tags: games, greedy, sortings Solve time: 6m 31s Verified: no Solution Problem Understanding We are given a list of items with integer costs, and two players, Alice and Bob, take turns picking items starting with Alice. After all items are taken, the score is the total cost Alice collected minus the total cost Bob collected. Alice tries to maximize this score, Bob tries...

CF 1994H - Fortnite

CF 1994H - Fortnite Rating: 3500 Tags: combinatorics, constructive algorithms, games, greedy, hashing, interactive, math, number theory, strings Solve time: 2m 4s Verified: no Solution Exploration The first problem asks whether an infinite sequence of perfect squares $(a_n^2)$ can exist such that each term starting from the third satisfies the Fibonacci-type recurrence $a_n^2 = a_{n-1}^2 + a_{n-2}^2.$ Since squares grow faster than linearly and the recurrence is additive, the existence...

EPIC Institute of Technology Round Summer 2024 (Div. 1 + Div. 2)

EPIC Institute of Technology Round Summer 2024 (Div. 1 + Div. 2) Type: Div. 1+2 | Problems: 10 | Verified: 3/10 | Rating range: 800-3500 | Time: 29m 10s Problem Name Rating Tags Solve Time Verified A Upload More RAM 800 greedy, math 1m 39s ✗ B K-Sort 1000 greedy 6m 11s ✗ C Basil's Garden 1200 dp, greedy 2m 18s ✓ D World is Mine 1800 dp, games 5m...

CF 1987D - World is Mine

CF 1987D - World is Mine Rating: 1800 Tags: dp, games Solve time: 5m 18s Verified: no Solution Problem Understanding We have a two-player game between Alice and Bob played over a set of cakes, each with an integer tastiness. Alice goes first. On her turn, she can only take a cake with a tastiness strictly higher than any cake she has previously eaten, while Bob can take any remaining...

CF 1972B - Coin Games

CF 1972B - Coin Games Rating: 900 Tags: games Solve time: 3m 56s Verified: no Solution Problem Understanding We are given a circular arrangement of coins. Each coin is either facing up or facing down. Two players alternate turns, and on each turn a player must pick one coin that is currently facing up, remove it, and then flip its two neighbors. The circle shrinks as coins are removed, and...

Codeforces Round 941 (Div. 2)

Codeforces Round 941 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 1/6 | Rating range: 800-2900 | Time: 16m 6s Problem Name Rating Tags Solve Time Verified A Card Exchange 800 constructive-algorithms, games, greedy 4m 54s ✗ B Rectangle Filling 1100 constructive-algorithms, implementation 1m 34s ✓ C Everything Nim 1400 games, greedy 1m 43s ✗ D Missing Subsequence Sum 1800 constructive-algorithms, greedy, math 3m 24s ✗ E Folding...

CF 1966A - Card Exchange

CF 1966A - Card Exchange Rating: 800 Tags: constructive algorithms, games, greedy Solve time: 4m 54s Verified: no Solution Problem Understanding We are given a hand of cards, each labeled with a number, and a fixed integer $k$. The operation allowed is to take any $k$ identical cards and exchange them for $k-1$ cards of any number we choose. The goal is to reduce the total number of cards as...

CF 1966C - Everything Nim

CF 1966C - Everything Nim Rating: 1400 Tags: games, greedy Solve time: 1m 43s Verified: no Solution Problem Understanding We are asked to analyze a two-player game with multiple piles of stones. On a player's turn, they choose a number $k$ that does not exceed the smallest non-empty pile, then remove $k$ stones from every pile that still has stones. Players alternate moves, and the first player who cannot make...

CF 1944C - MEX Game 1

CF 1944C - MEX Game 1 Rating: 1300 Tags: constructive algorithms, games, greedy Solve time: 3m 29s Verified: yes Solution Problem Understanding Alice and Bob play on a multiset of numbers. Alice and Bob alternately remove elements from the array, with Alice moving first. The difference is that whenever Alice removes a value, she also keeps it in her personal array c , while Bob simply deletes a value. When...

CF 1929C - Sasha and the Casino

CF 1929C - Sasha and the Casino Rating: 1400 Tags: binary search, brute force, constructive algorithms, games, greedy, math Solve time: 2m 33s Verified: no Solution Problem Understanding Sasha plays a repeated betting game where each bet either multiplies his stake by a factor or loses it entirely. The only control he has is the size of each bet, and he is allowed to adapt it based on past outcomes....

Codeforces Round 814 (Div. 2)

Codeforces Round 814 (Div. 2) Div. 2 | 3 problems | 2/3 verified | Difficulty 800-1400 | 11m 59s # Problem Rating Tags Accepted Time ✓ A Chip Game 800 games, math 26,817 1m 39s ✓ B Mathematical Circus 800 constructive-algorithms, math 19,167 5m 53s C Fighting Tournament 1400 binary-search, data-structures, implementation 14,362 4m 27s ✓

Codeforces Round 893 (Div. 2)

Codeforces Round 893 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2600 | Time: 14m 40s Problem Name Rating Tags Solve Time Verified A Buttons 800 games, greedy, math 1m 16s ✓ B The Walkway 1500 brute-force, dp, greedy 6m 1s ✗ C Yet Another Permutation Problem 1000 constructive-algorithms, greedy, math 1m 45s ✗ D Trees and Segments 2200 brute-force, data-structures, dp 3m 13s...

CF 1858A - Buttons

CF 1858A - Buttons Rating: 800 Tags: games, greedy, math Solve time: 1m 16s Verified: yes Solution Problem Understanding Two players alternate turns removing objects from a shared pool. Each object is a “button” with a restriction: some buttons can only be taken by Anna, some only by Katie, and some are flexible and can be taken by either player. Anna always moves first, and a player loses immediately when...

CF 1860C - Game on Permutation

CF 1860C - Game on Permutation Rating: 1400 Tags: data structures, dp, games, greedy Solve time: 1m 56s Verified: no Solution Problem Understanding We are given a permutation and a game played on its positions. The chip starts nowhere. Alice begins by choosing any position and placing the chip there. After that, players alternate moving the chip. From position i , the chip may move only to a position j...

Codeforces Round 792 (Div. 1 + Div. 2)

Codeforces Round 792 (Div. 1 + Div. 2) Type: Div. 1+2 | Problems: 8 | Verified: 2/8 | Rating range: 800-3400 | Time: 16m 54s Problem Name Rating Tags Solve Time Verified A Digit Minimization 800 constructive-algorithms, games, math 1m 57s ✓ B Z mod X = C 800 constructive-algorithms, math 2m 10s ✗ C Column Swapping 1400 brute-force, constructive-algorithms, greedy 2m ✓ D Traps 1700 constructive-algorithms, greedy, sortings 2m...

CF 1864E - Guess Game

CF 1864E - Guess Game Rating: 2100 Tags: bitmasks, data structures, games, math, probabilities, sortings, strings, trees Solve time: 2m 9s Verified: no Solution Problem Understanding We are given a multiset of integers, and we repeatedly imagine picking two positions independently, forming an ordered pair of values $(a, b)$. Along with $a$ and $b$, both players also learn the bitwise OR $x = a \mid b$. Alice and Bob know...

CF 1866I - Imagination Castle

CF 1866I - Imagination Castle Rating: 2300 Tags: dp, games, two pointers Solve time: 1m 42s Verified: yes Solution Problem Understanding We are given a grid with $N$ rows and $M$ columns. A game piece starts at the top-left cell $(1,1)$. From any cell, the piece can move either to the right within the same row or downward within the same column, but never left or up. Each move can...

Codeforces Round 897 (Div. 2)

Codeforces Round 897 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 1/7 | Rating range: 800-2700 | Time: 13m 50s Problem Name Rating Tags Solve Time Verified A green_gold_dog, array and permutation 800 constructive-algorithms, sortings 1m 34s ✗ B XOR Palindromes 1100 bitmasks, constructive-algorithms, strings 4m 6s ✗ C Salyg1n and the MEX Game 1300 constructive-algorithms, data-structures, games 1m 43s ✗ D Cyclic Operations 1800 brute-force, constructive-algorithms, dfs-and-similar...

CF 1867C - Salyg1n and the MEX Game

CF 1867C - Salyg1n and the MEX Game Rating: 1300 Tags: constructive algorithms, data structures, games, greedy, interactive Solve time: 1m 43s Verified: no Solution Problem Understanding We are given a sorted set of distinct integers. We do not control this set directly; instead, we interact with an opponent through moves that change it. Each move we either insert a new number into the set or allow Bob to remove...

CF 1873H - Mad City

CF 1873H - Mad City Rating: 1700 Tags: dfs and similar, dsu, games, graphs, shortest paths, trees Solve time: 1m 48s Verified: no Solution Problem Understanding We are asked to determine if one player, Valeriu, can indefinitely avoid being caught by another player, Marcel, in a city modeled as a connected graph with exactly $n$ buildings and $n$ roads. Each building is a node, and each road is an undirected...

Codeforces Round 901 (Div. 1)

Codeforces Round 901 (Div. 1) Type: Div. 1 | Problems: 7 | Verified: 3/7 | Rating range: 1200-3500 | Time: 15m 25s Problem Name Rating Tags Solve Time Verified A Jellyfish and Game 1200 brute-force, games, greedy 1m 59s ✓ B Jellyfish and Math 2400 bitmasks, brute-force, dfs-and-similar 2m 26s ✓ C Jellyfish and EVA 2300 dp, graphs, greedy 1m 57s ✗ D Jellyfish and Miku 2800 divide-and-conquer, dp, math...

CF 1874A - Jellyfish and Game

CF 1874A - Jellyfish and Game Rating: 1200 Tags: brute force, games, greedy, implementation Solve time: 1m 59s Verified: yes Solution Problem Understanding We have two players, Jellyfish and Gellyfish, each with a collection of green apples. Jellyfish has n apples with values stored in array a , and Gellyfish has m apples with values stored in array b . They play a game for k rounds. On odd-numbered rounds,...

CF 1895E - Infinite Card Game

CF 1895E - Infinite Card Game Rating: 2300 Tags: binary search, brute force, data structures, dfs and similar, dp, dsu, games, graphs, greedy, sortings, two pointers Solve time: 1m 54s Verified: no Solution Problem Understanding Each test case describes two players who each own a fixed set of cards. Every card has two numbers, an attack and a defence. A card can defeat another card if its attack is strictly...

Codeforces Round 909 (Div. 3)

Codeforces Round 909 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 5/7 | Rating range: 800-1900 | Time: 12m 9s Problem Name Rating Tags Solve Time Verified A Game with Integers 800 games, math, number-theory 1m 31s ✓ B 250 Thousand Tons of TNT 1100 brute-force, implementation, number-theory 2m 22s ✓ C Yarik and Array 1100 dp, greedy, two-pointers 1m 37s ✓ D Yarik and Musical Notes 1300...

CF 1899A - Game with Integers

CF 1899A - Game with Integers Rating: 800 Tags: games, math, number theory Solve time: 1m 31s Verified: yes Solution Problem Understanding We are asked to analyze a simple two-player game with integers. The game starts with a number $n$. Vanya moves first, and each player can either increment or decrement the number by 1 on their turn. Vanya wins immediately if, after his move, the number becomes divisible by...

CF 1906G - Grid Game 2

CF 1906G - Grid Game 2 Rating: 2900 Tags: games, number theory Solve time: 2m 21s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game played on an enormous grid of size $10^9 \times 10^9$. Each cell can be either black or white. Initially, only $N$ specific cells are black, and all others are white. Players take turns choosing a black cell. When a cell $(r,...

CF 1914E1 - Game with Marbles (Easy Version)

CF 1914E1 - Game with Marbles (Easy Version) Rating: 1400 Tags: brute force, games, greedy, sortings Solve time: 2m 34s Verified: yes Solution Problem Understanding Each color is an independent pile of marbles owned by both players. A move chooses a color that still exists on both sides. Suppose color i is chosen by Alice. Alice throws away exactly one of her marbles of that color, while Bob loses all...

CF 1914E2 - Game with Marbles (Hard Version)

CF 1914E2 - Game with Marbles (Hard Version) Rating: 1400 Tags: games, greedy, sortings Solve time: 2m 43s Verified: no Solution Problem Understanding Alice and Bob each have collections of marbles in $n$ colors. Alice's collection is represented as an array $a$, and Bob's as an array $b$, where $a_i$ and $b_i$ denote the number of marbles of color $i$ each player has. They play a turn-based game starting with...

Good Bye 2023

Good Bye 2023 Type: Special | Problems: 9 | Verified: 5/9 | Rating range: 800-3500 | Time: 14m 35s Problem Name Rating Tags Solve Time Verified A 2023 800 constructive-algorithms, implementation, math 2m 35s ✓ B Two Divisors 1000 constructive-algorithms, math, number-theory 38s ✗ C Training Before the Olympiad 1200 constructive-algorithms, games, greedy 1m 52s ✗ D Mathematical Problem 1700 brute-force, constructive-algorithms, geometry 38s ✗ E Happy Life in University...

CF 1916C - Training Before the Olympiad

CF 1916C - Training Before the Olympiad Rating: 1200 Tags: constructive algorithms, games, greedy, implementation, math Solve time: 1m 52s Verified: no Solution Problem Understanding We are given an array and asked to repeatedly reduce it until only one number remains. A move picks two elements, removes them, and inserts a new value derived from their sum: take the average of the pair, round it down, and then multiply by...

Hello 2024

Hello 2024 Type: Special | Problems: 9 | Verified: 3/9 | Rating range: 800-3500 | Time: 19m 25s Problem Name Rating Tags Solve Time Verified A Wallet Exchange 800 games, math 2m 5s ✓ B Plus-Minus Split 800 greedy 1m 58s ✓ C Grouping Increases 1400 data-structures, dp, greedy 2m 56s ✓ D 01 Tree 2100 constructive-algorithms, data-structures, dsu 46s ✗ E Counting Prefixes 2600 combinatorics, constructive-algorithms, dp 2m 42s...

CF 1919G - Tree LGM

CF 1919G - Tree LGM Rating: 3500 Tags: constructive algorithms, divide and conquer, games, trees Solve time: 1m 6s Verified: no Solution Problem Understanding We are asked to reconstruct a tree from a matrix of game outcomes. Each entry s[i][j] indicates whether the first player can force a win when the tree is rooted at vertex i and the coin starts at vertex j . A vertex can only move...

CF 1919A - Wallet Exchange

CF 1919A - Wallet Exchange Rating: 800 Tags: games, math Solve time: 2m 5s Verified: yes Solution Problem Understanding Alice and Bob each start with a wallet containing some number of coins. On every turn, the current player may either keep the wallets as they are or swap the two wallets. After that choice, they must remove exactly one coin from the wallet they currently hold. A move is legal...

Codeforces Round 919 (Div. 2)

Codeforces Round 919 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 3/7 | Rating range: 800-3000 | Time: 12m 20s Problem Name Rating Tags Solve Time Verified A Satisfying Constraints 800 brute-force, greedy, math 2m 3s ✓ B Summation Game 1100 games, greedy, math 1m 49s ✓ C Partitioning the Array 1600 brute-force, math, number-theory 48s ✗ D Array Repetition 1900 binary-search, brute-force, dsu 1m 18s ✓ E...

CF 1920B - Summation Game

CF 1920B - Summation Game Rating: 1100 Tags: games, greedy, math, sortings Solve time: 1m 49s Verified: yes Solution Problem Understanding We are asked to simulate a two-step game played on an array of positive integers. The first player, Alice, can remove up to $k$ elements. She wants the final sum of the array to be as large as possible. The second player, Bob, can then flip up to $x$...

CF 1921E - Eat the Chip

CF 1921E - Eat the Chip Rating: 1600 Tags: brute force, games, greedy, math Solve time: 2m 27s Verified: no Solution Problem Understanding We have a two-player game on a rectangular grid with height h and width w . Alice’s chip starts at (x_a, y_a) and can move down, down-left, or down-right. Bob’s chip starts at (x_b, y_b) and moves up, up-left, or up-right. Alice goes first, and a player...

Codeforces Round 1034 (Div. 3)

Codeforces Round 1034 (Div. 3) Div. 3 | 7 problems | 2/7 verified | Difficulty 800-2100 | 12m 37s # Problem Rating Tags Accepted Time ✓ A Blackboard Game 800 math 41,674 1m 37s ✓ B Tournament 800 greedy 34,895 1m 44s ✓ C Prefix Min and Suffix Max 1000 brute-force, data-structures 30,865 1m 35s D Binary String Battle 1200 constructive-algorithms, games, greedy 21,881 1m 28s E MEX Count 1400...

Codeforces Round 1067 (Div. 2)

Codeforces Round 1067 (Div. 2) Div. 2 | 7 problems | 2/7 verified | Difficulty 800-3000 | 10m 44s # Problem Rating Tags Accepted Time ✓ A Suspension 800 constructive-algorithms, greedy, math 23,377 1m 11s ✓ B Split 1200 constructive-algorithms, greedy, math 13,932 1m 47s C Annoying Game 1400 dp, games, greedy 11,047 1m 25s ✓ D Palindrome Flipping 2000 brute-force, constructive-algorithms, graphs 3,279 1m 44s E Sink 2600 data-structures,...

Codeforces Global Round 29 (Div. 1 + Div. 2)

Codeforces Global Round 29 (Div. 1 + Div. 2) Div. 1+2 | 10 problems | 1/10 verified | Difficulty 800-3500 | 20m 3s # Problem Rating Tags Accepted Time ✓ A Shortest Increasing Path 800 constructive-algorithms, greedy 18,624 1m 57s B Multiple Construction 1000 constructive-algorithms 16,950 1m 37s C Rabbits 1500 constructive-algorithms, dp, greedy 9,737 1m 41s D Game on Array 1700 games, greedy 7,482 2m 14s E Maximum OR...

Squarepoint Challenge (Codeforces Round 1055, Div. 1 + Div. 2)

Squarepoint Challenge (Codeforces Round 1055, Div. 1 + Div. 2) Div. 1+2 | 9 problems | 1/9 verified | Difficulty 800-3500 | 25m 17s # Problem Rating Tags Accepted Time ✓ A Increase or Smash 800 greedy, implementation 22,297 5m 19s B Catching the Krug 1300 games 12,846 3m 8s C Triple Removal 1400 data-structures, greedy, math 12,208 2m 7s D Division Versus Addition 1700 games, greedy, math 6,743 1m...

April Fools Day Contest 2025

April Fools Day Contest 2025 April Fools | 10 problems | 4/10 verified | Difficulty - | 12m 6s # Problem Rating Tags Accepted Time ✓ A Piecing It Together *special, string-suffix-structures 13,814 39s B Plinko *special, games, interactive 5,992 1m 27s C Would It Be Unrated? *special, binary-search, brute-force 3,744 1m 3s ✓ D Where Am I? *special, geometry 5,301 32s E Pair Count *special, number-theory 785 1m 32s...

XIX Open Olympiad in Informatics - Final Stage, Day 1 (Unrated, Online Mirror, IOI rules)

XIX Open Olympiad in Informatics - Final Stage, Day 1 (Unrated, Online Mirror, IOI rules) ICPC/IOI | 4 problems | 3/4 verified | Difficulty 1800-3300 | 3m 34s # Problem Rating Tags Accepted Time ✓ A Alice, Bob, And Two Arrays 3300 *special, data-structures, dp 37 55s ✓ B Arithmetic Exercise 2600 *special, data-structures, dp 155 1m 2s ✓ C Dreaming Is Not Harmful 2300 *special 222 49s D Cute...

Codeforces Round 996 (Div. 2)

Codeforces Round 996 (Div. 2) Div. 2 | 6 problems | 1/6 verified | Difficulty 800-3200 | 10m 14s # Problem Rating Tags Accepted Time ✓ A Two Frogs 800 constructive-algorithms, games, greedy 33,635 1m 26s ✓ B Crafting 1000 constructive-algorithms, greedy, sortings 27,277 1m 35s C The Trail 1400 brute-force, constructive-algorithms, greedy 17,241 1m 44s D Scarecrow 2000 greedy, implementation, math 4,366 1m 43s E Haystacks 2800 brute-force, constructive-algorithms,...

Codeforces Round 1023 (Div. 2)

Codeforces Round 1023 (Div. 2) Div. 2 | 7 problems | 1/7 verified | Difficulty 800-2800 | 11m 20s # Problem Rating Tags Accepted Time ✓ A LRC and VIP 800 greedy, number-theory 22,200 1m 20s B Apples in Boxes 1100 games, greedy, math 19,796 1m 38s ✓ C Maximum Subarray Sum 1500 binary-search, constructive-algorithms, dp 12,087 1m 39s D Apple Tree Traversing 2100 brute-force, dfs-and-similar, greedy 3,553 1m 32s...

Codeforces Round 992 (Div. 2)

Codeforces Round 992 (Div. 2) Div. 2 | 6 problems | 1/6 verified | Difficulty 800-2700 | 13m 11s # Problem Rating Tags Accepted Time ✓ A Game of Division 800 games, math 24,432 1m 17s B Paint a Strip 1000 constructive-algorithms, greedy, math 24,099 2m 28s C Ordered Permutations 1600 bitmasks, combinatorics, constructive-algorithms 10,776 2m 2s D Non Prime Tree 1900 brute-force, constructive-algorithms, dfs-and-similar 5,847 3m 17s E Control...

Educational Codeforces Round 172 (Rated for Div. 2)

Educational Codeforces Round 172 (Rated for Div. 2) Div. 2 | 6 problems | 0/6 verified | Difficulty 800-2900 | 13m 59s # Problem Rating Tags Accepted Time ✓ A Greedy Monocarp 800 greedy, sortings 20,853 1m 36s B Game with Colored Marbles 900 games, greedy 19,484 2m 26s C Competitive Fishing 1800 greedy 8,643 2m 9s D Recommendations 1900 data-structures, implementation, sortings 5,233 3m 15s E Vertex Pairs 2900...

CF 1931E - Anna and the Valentine's Day Gift

CF 1931E - Anna and the Valentine's Day Gift Rating: 1400 Tags: games, greedy, math, sortings Solve time: 2m 10s Verified: no Solution Problem Understanding The game begins with a list of integers. Anna moves first by reversing the digits of any number, which can increase or decrease its value depending on the digits. Sasha moves second by concatenating any two numbers, reducing the list size by one. The game...

CF 1934D2 - XOR Break --- Game Version

CF 1934D2 - XOR Break --- Game Version Rating: 2400 Tags: bitmasks, games, greedy, interactive Solve time: 1m 52s Verified: no Solution Problem Understanding We are given a starting number and two players who alternately “decompose” it. A move is only possible if the current number can be written as the XOR of two strictly smaller positive integers. If such a split exists, the active player chooses a valid split,...

CF 1939D - Big Persimmon

CF 1939D - Big Persimmon Rating: - Tags: *special, dp, games Solve time: 33s Verified: no Solution Before I start, can you confirm if the input consists of multiple test cases, or just a single test case per execution? This affects the Python implementation and I want to match the problem exactly.

Helvetic Coding Contest 2024 online mirror (teams allowed, unrated)

Helvetic Coding Contest 2024 online mirror (teams allowed, unrated) Type: Special | Problems: 21 | Verified: 6/21 | Rating range: 1000-3100 | Time: 47m 10s Problem Name Rating Tags Solve Time Verified A1 Balanced Shuffle (Easy) 1000 implementation, sortings 2m 8s ✓ A2 Balanced Unshuffle (Medium) 2400 brute-force, constructive-algorithms, trees 2m 43s ✗ A3 Balanced Unshuffle (Hard) 2400 constructive-algorithms, trees 2m 8s ✗ B1 Exact Neighbours (Easy) 1900 constructive-algorithms 1m...

CF 1970C3 - Game on Tree (Hard)

CF 1970C3 - Game on Tree (Hard) Rating: 1900 Tags: dfs and similar, dp, games, trees Solve time: 1m 59s Verified: yes Solution Problem Understanding We are given a tree of n nodes, and multiple rounds of a two-player game. In each round, a stone starts on one node. Players alternate moves, moving the stone to an unactivated neighbor and marking that neighbor as activated. The player who cannot move...

CF 1970C2 - Game on Tree (Medium)

CF 1970C2 - Game on Tree (Medium) Rating: 1700 Tags: dfs and similar, dp, games, trees Solve time: 2m Verified: yes Solution Problem Understanding We are given a tree where every node is initially unused. A single stone is placed on a chosen starting node. From that moment, players alternate moves, starting with Ron. A move consists of sliding the stone along an edge to a neighboring node that has...

CF 1970C1 - Game on Tree (Easy)

CF 1970C1 - Game on Tree (Easy) Rating: 1400 Tags: games Solve time: 1m 18s Verified: yes Solution Problem Understanding The structure we are given is not an arbitrary tree in the usual sense, but a very restricted one: it has exactly two leaves. That means every node has degree at most two, except possibly some internal nodes, and the whole graph is essentially a single chain. In other words,...

Codeforces Round 960 (Div. 2)

Codeforces Round 960 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 1/7 | Rating range: 900-2800 | Time: 18m 31s Problem Name Rating Tags Solve Time Verified A Submission Bait 900 brute-force, games, greedy 3m 55s ✗ B Array Craft 1200 constructive-algorithms, greedy 2m 33s ✗ C Mad MAD Sum 1500 brute-force, greedy, math 2m 48s ✓ D Grid Puzzle 1800 bitmasks, brute-force, dp 2m 13s ✗ E1...

CF 1990A - Submission Bait

CF 1990A - Submission Bait Rating: 900 Tags: brute force, games, greedy, sortings Solve time: 3m 55s Verified: no Solution Problem Understanding We have a two-player game on an array of integers. Alice and Bob take turns, with Alice starting first. Initially, a variable mx is zero. On their turn, a player can choose an array element a[i] if it is at least mx , set mx to that value,...

CF 1991I - Grid Game

CF 1991I - Grid Game Rating: 3500 Tags: constructive algorithms, games, graph matchings, greedy, interactive Solve time: 2m 45s Verified: no Solution Problem Understanding We are asked to play an interactive game on a rectangular grid of size $n \times m$. Each cell must be filled with a unique integer from $1$ to $n \cdot m$. Once the grid is filled, the interactor and we take turns picking unchosen cells....

CF 1991H - Prime Split Game

CF 1991H - Prime Split Game Rating: 3300 Tags: bitmasks, dp, fft, games, math, number theory Solve time: 2m 11s Verified: no Solution Problem Understanding In this problem, Alice and Bob are playing a turn-based game with piles of stones. Each pile contains some number of stones, and a player on their turn must choose a number of piles to remove and an equal number of piles to split, where...

CF 1991E - Coloring Game

CF 1991E - Coloring Game Rating: 1900 Tags: constructive algorithms, dfs and similar, games, graphs, greedy, interactive Solve time: 3m 7s Verified: no Solution Problem Understanding We are asked to play a two-player game on a connected undirected graph where each vertex can be colored with one of three colors. The game proceeds in rounds equal to the number of vertices. In each round, the player Alice chooses two distinct...

EPIC Institute of Technology Round August 2024 (Div. 1 + Div. 2)

EPIC Institute of Technology Round August 2024 (Div. 1 + Div. 2) Type: Div. 1+2 | Problems: 10 | Verified: 3/10 | Rating range: 800-3500 | Time: 20m 9s Problem Name Rating Tags Solve Time Verified A Distanced Coloring 800 constructive-algorithms, implementation, math 1m 48s ✓ B Removals Game 1000 constructive-algorithms, games 3m ✓ C Black Circles 1200 brute-force, geometry, greedy 1m 22s ✗ D1 DFS Checker (Easy Version) 1900...

CF 2002B - Removals Game

CF 2002B - Removals Game Rating: 1000 Tags: constructive algorithms, games Solve time: 3m Verified: yes Solution Problem Understanding We have two players, Alice and Bob, each holding a permutation of the numbers from 1 to n. They will alternately remove elements from either end of their respective arrays. After n-1 turns, only one element remains in each array. If the remaining elements are equal, Bob wins; otherwise, Alice wins....

Codeforces Round 968 (Div. 2)

Codeforces Round 968 (Div. 2) Type: Div. 2 | Problems: 8 | Verified: 1/8 | Rating range: 800-2800 | Time: 20m 20s Problem Name Rating Tags Solve Time Verified A Turtle and Good Strings 800 greedy, strings 2m 1s ✗ B Turtle and Piggy Are Playing a Game 2 800 games, greedy, sortings 2m ✗ C Turtle and Good Pairs 1200 constructive-algorithms, greedy, sortings 2m 35s ✗ D1 Turtle and...

CF 2003B - Turtle and Piggy Are Playing a Game 2

CF 2003B - Turtle and Piggy Are Playing a Game 2 Rating: 800 Tags: games, greedy, sortings Solve time: 2m Verified: no Solution Problem Understanding We are given a sequence of numbers and two players who repeatedly shrink it until only one value remains at the front position. Each move removes one element, but before removing it, the left element of the chosen adjacent pair is updated. One player always...

CF 2005E2 - Subtangle Game (Hard Version)

CF 2005E2 - Subtangle Game (Hard Version) Rating: 2500 Tags: data structures, dp, games, greedy, implementation Solve time: 2m 40s Verified: no Solution Problem Understanding We have a sequence $a$ and an $n \times m$ matrix $b$. The game follows the sequence from left to right. On move $k$, the current player must choose a cell whose value equals $a_k$. If the chosen cell is $(r,c)$, the next move is...

CF 2005E1 - Subtangle Game (Easy Version)

CF 2005E1 - Subtangle Game (Easy Version) Rating: 2100 Tags: dp, games, greedy, implementation Solve time: 2m 15s Verified: no Solution Problem-Type Check This is a Type B (prove) problem. The solution correctly interprets the statement: it aims to prove that any triangle admitting a circle tangent to two sides and two medians must be isosceles. The proof addresses the exact hypothesis and derives the required equality of two sides....

Codeforces Round 969 (Div. 1)

Codeforces Round 969 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 0/6 | Rating range: 1700-3500 | Time: 10m 11s Problem Name Rating Tags Solve Time Verified A Iris and Game on the Tree 1700 constructive-algorithms, dfs-and-similar, games 2m 11s ✗ B Iris and the Tree 1800 brute-force, data-structures, dfs-and-similar 1m 34s ✗ C Eri and Expanded Sets 2300 data-structures, divide-and-conquer, math 2m 53s ✗ D Iris and...

CF 2006A - Iris and Game on the Tree

CF 2006A - Iris and Game on the Tree Rating: 1700 Tags: constructive algorithms, dfs and similar, games, graphs, greedy, trees Solve time: 2m 11s Verified: no Solution Problem Understanding We are given a rooted tree with root fixed at vertex 1. Each vertex carries a label that is either 0, 1, or unknown. The unknown entries are the only things we are allowed to choose during the game, and...

CF 2013F1 - Game in Tree (Easy Version)

CF 2013F1 - Game in Tree (Easy Version) Rating: 2700 Tags: binary search, brute force, data structures, dp, games, greedy, implementation, trees Solve time: 1m 36s Verified: yes Solution Problem Understanding We are given a tree. One player, Alice, always starts at vertex 1. The other player, Bob, starts at a vertex that lies on a fixed simple path between two vertices u and v. In this easy version u...

CF 2027E1 - Bit Game (Easy Version)

CF 2027E1 - Bit Game (Easy Version) Rating: 2800 Tags: bitmasks, brute force, games, math Solve time: 1m 17s Verified: no Solution Problem Understanding Each test case gives us several independent piles of stones. Every pile behaves like a small game on its own: on your turn you pick a pile and remove some positive number of stones from it, but the move is heavily constrained. If the pile currently...

CF 2028E - Alice's Adventures in the Rabbit Hole

CF 2028E - Alice's Adventures in the Rabbit Hole Rating: 2300 Tags: combinatorics, dfs and similar, dp, games, greedy, math, probabilities, trees Solve time: 1m 23s Verified: no Solution Problem Understanding We are given a tree with n vertices where vertex 1 is considered the exit of the rabbit hole, and Alice starts at some vertex v . Each turn a fair coin is flipped. On heads, Alice chooses an...

Refact.ai Match 1 (Codeforces Round 985)

Refact.ai Match 1 (Codeforces Round 985) Type: Special | Problems: 9 | Verified: 1/9 | Rating range: 800-3500 | Time: 18m 21s Problem Name Rating Tags Solve Time Verified A Set 800 greedy, math 1m 27s ✓ B Replacement 1100 constructive-algorithms, games, strings 1m 37s ✗ C New Rating 1700 binary-search, data-structures, dp 3m 19s ✗ D Cool Graph 1900 constructive-algorithms, data-structures, dfs-and-similar 1m 37s ✗ E Common Generator 2100...

CF 2029B - Replacement

CF 2029B - Replacement Rating: 1100 Tags: constructive algorithms, games, strings Solve time: 1m 37s Verified: no Solution Problem Understanding We are given a binary string s of length n and another binary string r of length n-1 . The problem describes a game where we repeatedly shorten s by replacing any adjacent pair of differing bits with the next character in r . On each turn, we must pick...

Codeforces Round 979 (Div. 2)

Codeforces Round 979 (Div. 2) Type: Div. 2 | Problems: 8 | Verified: 5/8 | Rating range: 800-3100 | Time: 13m 10s Problem Name Rating Tags Solve Time Verified A A Gift From Orangutan 800 constructive-algorithms, greedy, math 1m 56s ✓ B Minimise Oneness 800 combinatorics, constructive-algorithms, games 1m 39s ✓ C A TRUE Battle 1100 brute-force, games, greedy 1m 39s ✓ D QED's Favorite Permutation 1700 data-structures, implementation, sortings...

CF 2030C - A TRUE Battle

CF 2030C - A TRUE Battle Rating: 1100 Tags: brute force, games, greedy Solve time: 1m 39s Verified: yes Solution Problem Understanding We are given a binary string where each character is a fixed boolean value. The players do not change these values. Their only action is deciding where to place binary operators between adjacent positions, specifically choosing either AND or OR for each gap. Since there are n characters,...

CF 2032F - Peanuts

CF 2032F - Peanuts Rating: 2700 Tags: combinatorics, dp, games, math Solve time: 1m 59s Verified: no Solution Problem Understanding We are given a sequence of pockets, each containing a positive number of peanuts. Alice can partition the sequence into contiguous boxes of pockets. Once the boxes are fixed, Alice and Jack play a sequential game where on their turn a player must remove a positive number of peanuts from...

Atto Round 1 (Codeforces Round 1041, Div. 1 + Div. 2)

Atto Round 1 (Codeforces Round 1041, Div. 1 + Div. 2) Type: Div. 1+2 | Problems: 9 | Verified: 2/9 | Rating range: 800-3500 | Time: 21m 47s Problem Name Rating Tags Solve Time Verified A Mix Mex Max 800 constructive-algorithms, greedy, math 3m 30s ✗ B Hamiiid, Haaamid... Hamid? 1300 games, greedy 2m 6s ✓ C Trip Shopping 1400 games, greedy, sortings 2m 11s ✗ D Root was Built...

CF 2127C - Trip Shopping

CF 2127C - Trip Shopping Rating: 1400 Tags: games, greedy, sortings Solve time: 2m 11s Verified: no Solution Problem Understanding We are given two arrays of integers, a and b , representing prices of items in two categories. The game consists of k rounds. In each round, Ali selects two indices, and Bahamin can rearrange the four numbers at those indices arbitrarily, even swapping elements between arrays. After all rounds,...

CF 2127B - Hamiiid, Haaamid... Hamid?

CF 2127B - Hamiiid, Haaamid... Hamid? Rating: 1300 Tags: games, greedy Solve time: 2m 6s Verified: yes Solution Problem Understanding We are given a one-dimensional grid of length n , with some cells containing walls and others empty. Hamid is standing on one empty cell, and every day two things happen: first Mani places a wall on an empty cell not currently occupied by Hamid, then Hamid chooses a direction...

CF 2115D - Gellyfish and Forget-Me-Not

CF 2115D - Gellyfish and Forget-Me-Not Rating: 2900 Tags: bitmasks, dp, games, greedy, math Solve time: 3m 4s Verified: no Solution Correct reasoning For two odd-index cells $A(x_1,y_1)$, $B(x_2,y_2)$, we need to count the number of cells $C$ such that: $C$ is adjacent to $A$ $C$ is adjacent to $B$ and $A \ne B \ne C$ On a grid, this intersection has a known structure: If $A$ and $B$ differ...

Codeforces Round 998 (Div. 3)

Codeforces Round 998 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 4/7 | Rating range: 800-2400 | Time: 11m 10s Problem Name Rating Tags Solve Time Verified A Fibonacciness 800 brute-force 1m 5s ✓ B Farmer John's Card Game 1000 greedy, sortings 1m 21s ✓ C Game of Mathletes 900 games, greedy, sortings 1m 18s ✓ D Subtract Min Sort 1100 greedy 1m 48s ✗ E Graph Composition...

2024-2025 ICPC, NERC, Southern and Volga Russian Regional Contest (Unrated, Online Mirror, ICPC Rules, Preferably Teams)

2024-2025 ICPC, NERC, Southern and Volga Russian Regional Contest (Unrated, Online Mirror, ICPC Rules, Preferably Teams) Type: ICPC/IOI | Problems: 14 | Verified: 6/14 | Rating range: 800-3000 | Time: 27m 19s Problem Name Rating Tags Solve Time Verified A Bonus Project 1400 games, greedy 2m 9s ✗ B Make It Equal 2100 binary-search, brute-force, greedy 2m 4s ✗ C DIY 1400 data-structures, geometry, greedy 2m 19s ✗ D Divide...

CF 2038A - Bonus Project

CF 2038A - Bonus Project Rating: 1400 Tags: games, greedy Solve time: 2m 9s Verified: no Solution Problem Understanding We have a team of engineers, each with a promised bonus and a personal cost for doing one unit of work. The team needs to complete a project that requires exactly $k$ units of work, and every engineer will decide individually how much to contribute. The amount each engineer contributes, $c_i$,...

CF 2040A - Game of Division

CF 2040A - Game of Division Rating: 800 Tags: games, math Solve time: 1m 17s Verified: no Solution Problem Understanding We are looking at a decision problem where one player tries to “trap” another player using modular arithmetic on array values. We are given an array of integers. The first player picks a single position in the array and commits to that value. After seeing this choice, the second player...

CF 2042B - Game with Colored Marbles

CF 2042B - Game with Colored Marbles Rating: 900 Tags: games, greedy Solve time: 2m 26s Verified: no Solution Problem Understanding We are asked to compute Alice's final score in a sequential marble-taking game. There is a collection of n marbles, each with a specific color. Alice and Bob alternate turns, starting with Alice. Each turn consists of removing one marble. Alice’s score is calculated based on colors she owns:...

CF 2043F - Nim

CF 2043F - Nim Rating: 2700 Tags: bitmasks, brute force, combinatorics, dp, games, greedy, implementation, shortest paths Solve time: 2m 2s Verified: no Solution Problem Understanding We are asked to consider multiple rounds of the game Nim played on contiguous subarrays of an array of integers. Each integer represents a pile of stones. The game follows standard Nim rules: two players take turns removing at least one stone from any...

CF 2045F - Grid Game 3-angle

CF 2045F - Grid Game 3-angle Rating: 3000 Tags: games, math Solve time: 1m 48s Verified: no Solution Problem Understanding We are given a triangular grid of size $N$, where row $r$ has $r$ cells. Certain cells initially contain some stones. Two players, Anda and Kamu, alternate turns, starting with Anda. On a turn, a player picks a cell with at least one stone, removes between $1$ and $K$ stones,...

CF 2053E - Resourceful Caterpillar Sequence

CF 2053E - Resourceful Caterpillar Sequence Rating: 1900 Tags: dfs and similar, dp, games, graphs, greedy, trees Solve time: 1m 48s Verified: no Solution Problem Understanding We are given a tree. Two endpoints are chosen, a head $p$ and a tail $q$, and the only vertices that matter are those on the unique path between them. The game is a two-player process where Nora controls the head side and Aron...

CF 2055A - Two Frogs

CF 2055A - Two Frogs Rating: 800 Tags: constructive algorithms, games, greedy, math Solve time: 1m 26s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game played on a row of lilypads numbered from 1 to $n$. Alice starts on lilypad $a$ and Bob on lilypad $b$, and they take turns jumping either one step left or right. A frog loses if it cannot jump to...

CF 2060C - Game of Mathletes

CF 2060C - Game of Mathletes Rating: 900 Tags: games, greedy, sortings, two pointers Solve time: 1m 18s Verified: yes Solution Problem Understanding We are given an array of integers written on a board. The game repeatedly removes two numbers per round, but the order matters: Alice removes one number first with the intent of making Bob fail to form a good pair later, while Bob responds by removing another...

CF 2062E2 - The Game (Hard Version)

CF 2062E2 - The Game (Hard Version) Rating: 3000 Tags: data structures, dfs and similar, games, graphs, implementation, trees Solve time: 1m 38s Verified: no Solution Problem Understanding We are given a tree with n nodes rooted at node 1 , and each node has an associated integer weight. Cirno and Daiyousei play a sequential game on this tree. On her turn, a player selects a node that has a...

CF 2062E1 - The Game (Easy Version)

CF 2062E1 - The Game (Easy Version) Rating: 2000 Tags: data structures, dfs and similar, games, graphs, greedy, trees Solve time: 1m 55s Verified: no Solution Problem Understanding We are given a rooted tree where each node has a weight. Two players play a turn-based game. On each move, a player chooses a node whose weight is strictly larger than the weight chosen in the previous move and deletes its...

CF 2070E - Game with Binary String

CF 2070E - Game with Binary String Rating: 2200 Tags: constructive algorithms, data structures, divide and conquer, games, greedy, math Solve time: 1m 34s Verified: no Solution Problem Understanding We are given a binary string and we look at every contiguous substring. For each substring, a two-player game is played on the characters of that substring, where each move removes exactly two adjacent characters. Adjacency is cyclic in the sense...

CF 2079A - Alice, Bob, And Two Arrays

CF 2079A - Alice, Bob, And Two Arrays Rating: 3300 Tags: *special, data structures, dp, games Solve time: 55s Verified: yes Solution Problem Understanding We have two players, Alice and Bob, each with their own array of integers of the same length. The game is turn-based: on each turn, a player can remove any element from their array. The score a player earns on a turn is the sum of...

CF 2084G1 - Wish Upon a Satellite (Easy Version)

CF 2084G1 - Wish Upon a Satellite (Easy Version) Rating: 2600 Tags: dp, games Solve time: 1m 44s Verified: no Solution Problem Understanding We are given a partially filled permutation of length $n$, where some entries are zero, representing missing numbers. The goal is to fill in the zeros with the remaining numbers from $1$ to $n$ to form a complete permutation. Once we have a full permutation, we define...

CF 2089C1 - Key of Like (Easy Version)

CF 2089C1 - Key of Like (Easy Version) Rating: 2200 Tags: dp, games, math, probabilities Solve time: 1m 50s Verified: no Solution Problem Understanding In this problem, we are asked to simulate a sequential game where a group of n participants try to unlock l locks using exactly l valid keys. Each participant takes one turn at a time in a fixed cyclic order. On each turn, a participant chooses...

CF 2095B - Plinko

CF 2095B - Plinko Rating: - Tags: *special, games, interactive Solve time: 1m 27s Verified: no Solution Problem Understanding The problem is an interactive simulation of a simple Plinko game, where a ball drops through a triangular pegboard and eventually lands in one of ten numbered slots at the bottom. Each round of the game is labeled from Game 1 to Game 10 . For each round, you must output...

CF 2104C - Card Game

CF 2104C - Card Game Rating: 1100 Tags: brute force, constructive algorithms, games, greedy, math Solve time: 1m 19s Verified: yes Solution Problem Understanding We are given a small card game where each card is uniquely labeled from 1 to n, and each card initially belongs to either Alice or Bob. The ownership is fixed at the start, but during the game cards can move between players depending on outcomes....

CF 2107B - Apples in Boxes

CF 2107B - Apples in Boxes Rating: 1100 Tags: games, greedy, math Solve time: 1m 38s Verified: yes Solution Problem Understanding We are given several independent games. In each game, there are multiple boxes of apples. On every move, a player removes exactly one apple from a single non-empty box. Tom always moves first, and players alternate turns until someone cannot move or until a move causes the configuration to...

CF 2123D - Binary String Battle

CF 2123D - Binary String Battle Rating: 1200 Tags: constructive algorithms, games, greedy Solve time: 1m 28s Verified: no Solution Problem Understanding We are given a binary string. Two players alternate moves, with Alice moving first. The game evolves by repeatedly rewriting parts of the string. On Alice’s move, she can pick any collection of exactly k positions anywhere in the string, not necessarily contiguous, and force all those positions...

Codeforces Round 969 (Div. 2)

Codeforces Round 969 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2300 | Time: 17m 28s Problem Name Rating Tags Solve Time Verified A Dora's Set 800 greedy, math, number-theory 2m 16s ✓ B Index and Maximum Value 900 data-structures, greedy 1m 31s ✓ C Dora and C++ 1500 math, number-theory 5m 16s ✗ D Iris and Game on the Tree 1700 games, graphs,...

CF 2137G - Cry Me a River

CF 2137G - Cry Me a River Rating: 2200 Tags: dfs and similar, dp, games, graphs Solve time: 1m 29s Verified: no Solution Problem Understanding We are given a directed acyclic graph with n nodes and m edges. Each node starts colored blue, and players Cry and River play a two-player token game. The token starts at a node s . Cry moves first, then River, and they alternate. Cry...

CF 2140C - Ultimate Value

CF 2140C - Ultimate Value Rating: 1500 Tags: data structures, games, greedy Solve time: 2m 6s Verified: yes Solution Problem Understanding We are given a game played on an array of integers where two players take turns performing a single action: either end the game immediately or swap two elements at positions $l$ and $r$, which adds $r-l$ to a running cost. The function we are trying to optimize is...

CF 2147D - Game on Array

CF 2147D - Game on Array Rating: 1700 Tags: games, greedy Solve time: 2m 14s Verified: no Solution Problem Understanding We are given a sequence of positive integers, representing a set of “tiles” with values. Two players, Alice and Bob, take turns picking a number that currently exists in the array. When a number x is picked, the player earns points equal to the count of that number in the...

CF 2152D - Division Versus Addition

CF 2152D - Division Versus Addition Rating: 1700 Tags: games, greedy, math Solve time: 1m 25s Verified: no Solution Problem Understanding We are given an array where every element starts at least 2, and two players repeatedly modify it until every value becomes 1. One player always reduces a chosen element by replacing it with half of its floor value, while the other always increases a chosen element by 1,...

CF 2152B - Catching the Krug

CF 2152B - Catching the Krug Rating: 1300 Tags: games Solve time: 3m 8s Verified: no Solution Problem Understanding We are asked to compute the maximum number of turns the Krug can survive against Doran on a square grid. The grid has coordinates from 0 to n in both rows and columns. The Krug moves first, either staying in place or moving to a vertically or horizontally adjacent cell. Doran...

CF 2155E - Mimo & Yuyu

CF 2155E - Mimo & Yuyu Rating: 2200 Tags: games, greedy, math Solve time: 3m 28s Verified: no Solution Problem Understanding We are asked to analyze a two-player game on an $n \times m$ grid. Each cell can contain tokens, and on a turn, a player picks a token and moves it along a sequence of adjacent cells that always steps leftwards in columns, ultimately depositing new tokens along that...

CF 2156E - Best Time to Buy and Sell Stock

CF 2156E - Best Time to Buy and Sell Stock Rating: 2500 Tags: binary search, brute force, data structures, dp, games, graphs, greedy Solve time: 1m 49s Verified: no Solution Problem Understanding We are given a list of numbers and two players who interact with it in a turn-based process. The key twist is that the final outcome is not chosen directly, but emerges from a game where one player...

CF 2157I - Hyper Smawk Bros

CF 2157I - Hyper Smawk Bros Rating: 3500 Tags: dp, games Solve time: 3m 13s Verified: no Solution Problem Understanding In Hyper Smawk Bros, two players take turns attacking a boss with health n . Each attack reduces the health by an integer damage x between 1 and m . The catch is that on your turn, you cannot repeat the exact damage your opponent used on the previous turn....

CF 2158C - Annoying Game

CF 2158C - Annoying Game Rating: 1400 Tags: dp, games, greedy Solve time: 1m 25s Verified: yes Solution Problem Understanding We are given an array $a$ and another array $b$ of the same length. Two players alternate turns for exactly $k$ moves. On each move, the current player picks an index and either adds or subtracts the corresponding value $b_i$ from $a_i$. After all moves are finished, we look at...

CF 2161A - Round Trip

CF 2161A - Round Trip Rating: 800 Tags: games, greedy, implementation, math Solve time: 1m 31s Verified: yes Solution Problem Understanding We are simulating a sequence of contest rounds where a participant can sometimes adjust their rating before each rated round. The key complication is that whether a round is rated for the participant depends on their current rating compared to a fixed threshold, and in rated rounds they are...

CF 2171C1 - Renako Amaori and XOR Game (easy version)

CF 2171C1 - Renako Amaori and XOR Game (easy version) Rating: 1100 Tags: bitmasks, games, greedy Solve time: 3m 41s Verified: no Solution Problem Understanding Each test case gives two binary arrays of equal length. On position $i$, there is a pair of bits $(a_i, b_i)$. During the game, players go through indices from left to right. At index $i$, exactly one action may happen: either the two values at...

CF 2171C2 - Renako Amaori and XOR Game (hard version)

CF 2171C2 - Renako Amaori and XOR Game (hard version) Rating: 1400 Tags: bitmasks, games, greedy Solve time: 1m 23s Verified: no Solution Problem Understanding We are asked to simulate a two-player game on two arrays of integers, a and b , each of length n . Players take turns: Ajisai moves on odd-numbered turns, Mai moves on even-numbered turns. On a player’s turn, they can swap the current element...

CF 2180H2 - Bug Is Feature (Conditional Version)

CF 2180H2 - Bug Is Feature (Conditional Version) Rating: 3500 Tags: games Solve time: 1m 41s Verified: yes Solution Problem Understanding Each game starts from three numbers forming an arithmetic progression, so the state can always be described as $(a, a+d, a+2d)$ with $d > 0$. The players repeatedly pick one coordinate and increase it, but the triple must remain an arithmetic progression after every move. The order is allowed...

CF 2180H1 - Bug Is Feature (Unconditional Version)

CF 2180H1 - Bug Is Feature (Unconditional Version) Rating: 3400 Tags: games Solve time: 1m 47s Verified: no Solution Working

CF 2181F - Fragmented Nim

CF 2181F - Fragmented Nim Rating: 1600 Tags: games Solve time: 1m 51s Verified: yes Solution Problem Understanding We are asked to analyze a variation of the classical game of Nim. In the original Nim, players take turns picking a pile and removing any number of stones. The player who takes the last stone wins. In this variant, the twist is that the player whose turn it is does not...

CF 2181B - Battle of Arrays

CF 2181B - Battle of Arrays Rating: 1400 Tags: data structures, games, greedy Solve time: 1m 55s Verified: no Solution Problem Understanding We are asked to simulate a turn-based game between Alice and Bob. Each player starts with an array of positive integers. On their turn, a player picks any element from their own array and applies it against the maximal element in the opponent's array. If the chosen element...

CF 2183A - Binary Array Game

CF 2183A - Binary Array Game Rating: 800 Tags: games Solve time: 1m 37s Verified: no Solution Problem Understanding We are given a binary array that evolves through a merging game. Two players, Alice and Bob, alternate turns. On each turn, a player selects a contiguous segment of length at least two, removes it, and replaces it with a single value derived from that segment. If the chosen segment contains...

CF 2187C - Jerry and Tom

CF 2187C - Jerry and Tom Rating: 2300 Tags: data structures, dfs and similar, dsu, games, graphs, greedy, trees Solve time: 2m 26s Verified: no Solution Problem Understanding We are asked to analyze a two-player game on a directed graph with $n$ vertices. The graph is almost a chain: for every vertex $u$ from 1 to $n-1$, there is an edge $u \to u+1$. On top of this, there are...

CF 2190B2 - Sub-RBS (Hard Version)

CF 2190B2 - Sub-RBS (Hard Version) Rating: 1900 Tags: dp, games, implementation, strings Solve time: 3m 32s Verified: no Solution Problem Understanding We are asked to compute a sum over all non-empty subsequences of a given bracket sequence. Each subsequence has a “score” defined as the length of its longest regular bracket subsequence that is strictly “better” than itself. A regular bracket sequence is one where the brackets match properly,...

CF 2190A - Sorting Game

CF 2190A - Sorting Game Rating: 1200 Tags: constructive algorithms, games, greedy Solve time: 1m 53s Verified: no Solution Problem Understanding We are asked to analyze a two-player game on a binary string, where Alice goes first and Bob follows, taking turns. On their turn, a player may select any strictly non-increasing subsequence of the string and rearrange it to be non-decreasing. In practice, this means finding a sequence of...

CF 2196A - Game with a Fraction

CF 2196A - Game with a Fraction Rating: 1200 Tags: games, math Solve time: 2m 40s Verified: no Solution Problem Understanding We are given two integers, $p$ and $q$, representing a fraction $\frac{p}{q}$. Alice and Bob play a turn-based game where on each turn a player can decrease $p$ by 1 (if $p > 0$) or decrease $q$ by 1 (if $q > 1$). Alice goes first. Bob wins immediately...

CF 2200E - Divisive Battle

CF 2200E - Divisive Battle Rating: 1500 Tags: games, greedy, math, number theory Solve time: 1m 41s Verified: no Solution Problem Understanding We are given an array of positive integers and two players who alternate turns, starting with Alice. The game evolves by either ending immediately if the current array is already non-decreasing, or by performing a single allowed operation on a chosen element. The only operation available is to...

CF 2203E - Probabilistic Card Game

CF 2203E - Probabilistic Card Game Rating: 2200 Tags: binary search, data structures, games, greedy, math, ternary search Solve time: 2m 1s Verified: no Solution Problem Understanding We are asked to compute the expected score for Bob in a turn-based card game where Alice and Bob play optimally. Each round, a new card is added to a deck. Once the deck has at least three cards, Alice selects a card,...

CF 2203D - Divisibility Game

CF 2203D - Divisibility Game Rating: 1700 Tags: brute force, games, greedy, number theory Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given two multisets, one called a and one called b . They define a game where players do not modify a at all, but gradually consume elements from b . On each turn, the current player picks a value x from a and a value...

CF 2206B - Subtree Removal Game

CF 2206B - Subtree Removal Game Rating: 2500 Tags: binary search, games, trees Solve time: 2m 20s Verified: yes Solution Problem Understanding We are given a rooted tree with nodes numbered from 1 to $n$, rooted at node 1. Each node may either have an integer written on it (leaves) or be empty (internal nodes). Two players play a game: on a turn, a player removes a subtree rooted at...

CF 2207D - Boxed Like a Fish

CF 2207D - Boxed Like a Fish Rating: 2200 Tags: dfs and similar, dp, games, shortest paths, trees Solve time: 1m 46s Verified: no Solution Problem Understanding We are given a tree where a token starts at a fixed non-leaf vertex. The goal is to determine whether this token can be guaranteed to reach any leaf vertex if two players act in turns. One player controls the token. Each turn,...

CF 2207B - One Night At Freddy's

CF 2207B - One Night At Freddy's Rating: 1600 Tags: games, greedy, sortings Solve time: 1m 48s Verified: no Solution Problem Understanding We are asked to simulate a night at Freddy Fazbear’s Pizzeria in terms of danger management. Each animatronic accumulates danger every second, and the night lasts for a fixed number of seconds. The player has a limited number of “flashlight actions” at predetermined times, each of which can...

CF 2208B - Cyclists

CF 2208B - Cyclists Rating: 1100 Tags: brute force, games, greedy, implementation, math, sortings Solve time: 2m 23s Verified: no Solution Problem Understanding We are given a deck of n cards, each with an energy cost. Bob wants to play a special "win-condition" card as many times as possible without exceeding a total energy budget m . On each turn, Bob can select a card from only the first k...

CF 2214J - Special Problem

CF 2214J - Special Problem Rating: - Tags: *special, brute force, games, interactive Solve time: 58s Verified: yes Solution Problem Understanding This problem presents an interactive game scenario where you have a hidden system generating some responses. The goal is to query the system in a structured way to deduce a hidden value or sequence. Typically, the input consists of queries you can make and the output is the system’s...

CF 2215F - Research

CF 2215F - Research Rating: 3500 Tags: games Solve time: 1m 40s Verified: no Solution Problem Understanding We are looking at a two-player deterministic game played on a deck that is mostly identical cards except for one special card. The special card, initially green, sits at a known position from the top. Each turn, a player removes a fixed number of cards from the top of the deck, can optionally...

Codeforces Round 1085 (Div. 1 + Div. 2)

Codeforces Round 1085 (Div. 1 + Div. 2) Div. 1+2 | 11 problems | 0/11 verified | Difficulty 800-3300 | 22m 3s # Problem Rating Tags Accepted Time ✓ A 1-1 800 greedy, strings 13,650 1m 54s B One Night At Freddy's 1600 games, greedy, sortings 5,785 1m 48s C Where's My Water? 1600 data-structures, divide-and-conquer, dp 5,420 2m 25s D Boxed Like a Fish 2200 dfs-and-similar, dp, games 2,106...

Codeforces Round 1084 (Div. 3)

Codeforces Round 1084 (Div. 3) Div. 3 | 8 problems | 2/8 verified | Difficulty 800-2600 | 14m 57s # Problem Rating Tags Accepted Time ✓ A Eating Game 800 greedy 28,042 1m 33s ✓ B Deletion Sort 800 bitmasks, brute-force, greedy 25,414 1m 32s C Specialty String 900 brute-force, greedy, strings 21,666 1m 33s ✓ D Portal 1300 greedy, sortings 11,758 2m 1s E Divisive Battle 1500 games, greedy,...

Codeforces Round 1086 (Div. 2)

Codeforces Round 1086 (Div. 2) Div. 2 | 6 problems | 2/6 verified | Difficulty 800-2700 | 14m # Problem Rating Tags Accepted Time ✓ A Bingo Candies 800 constructive-algorithms, math 20,130 1m 45s ✓ B Cyclists 1100 brute-force, games, greedy 13,623 2m 23s C Stamina and Tasks 1300 dp, greedy, math 11,031 1m 59s ✓ D1 Tree Orientation (Easy Version) 1800 constructive-algorithms, dfs-and-similar, dsu 4,190 3m 24s D2 Tree...

2026 ICPC Asia Pacific Championship - Online Mirror (Unrated, Online Mirror, ICPC Rules, Teams Preferred)

2026 ICPC Asia Pacific Championship - Online Mirror (Unrated, Online Mirror, ICPC Rules, Teams Preferred) ICPC/IOI | 13 problems | 3/13 verified | Difficulty 1300-3500 | 28m 52s # Problem Rating Tags Accepted Time ✓ A Compare Suffixes 3500 interactive 84 1m 54s B Subtree Removal Game 2500 binary-search, games, trees 347 2m 20s ✓ C Upside Down Dijkstra 2200 dfs-and-similar 625 2m 25s D Christmas Tree Un-decoration 2600 data-structures,...

Codeforces Round 1079 (Div. 1)

Codeforces Round 1079 (Div. 1) Div. 1 | 8 problems | 2/8 verified | Difficulty 1200-3300 | 16m 32s # Problem Rating Tags Accepted Time ✓ A Game with a Fraction 1200 games, math 15,791 2m 40s B Another Problem about Beautiful Pairs 1600 brute-force, math, two-pointers 8,565 1m 18s ✓ C1 Interactive Graph (Simple Version) 1800 binary-search, combinatorics, dfs-and-similar 3,584 1m 53s C2 Interactive Graph (Hard Version) 2000 combinatorics,...

Pinely Round 5 (Div. 1 + Div. 2)

Pinely Round 5 (Div. 1 + Div. 2) Div. 1+2 | 8 problems | 1/8 verified | Difficulty 800-3500 | 15m 15s # Problem Rating Tags Accepted Time ✓ A Round Trip 800 games, greedy, implementation 15,715 1m 31s ✓ B Make Connected 1700 brute-force, implementation 5,369 1m 35s C Loyalty 1200 constructive-algorithms, greedy, sortings 12,536 1m 51s D Locked Out 2100 binary-search, data-structures, dp 2,771 1m 44s E Left...

Codeforces Round 1065 (Div. 3)

Codeforces Round 1065 (Div. 3) Div. 3 | 9 problems | 3/9 verified | Difficulty 800-2400 | 17m 12s # Problem Rating Tags Accepted Time ✓ A Shizuku Hoshikawa and Farm Legs 800 brute-force, math 37,229 36s B Yuu Koito and Minimum Absolute Sum 900 math 27,072 1m 24s ✓ C1 Renako Amaori and XOR Game (easy version) 1100 bitmasks, games, greedy 19,223 3m 41s C2 Renako Amaori and XOR...

2025-2026 ICPC, NERC, Northern Eurasia Finals (Unrated, Online Mirror, ICPC Rules, Teams Preferred)

2025-2026 ICPC, NERC, Northern Eurasia Finals (Unrated, Online Mirror, ICPC Rules, Teams Preferred) ICPC/IOI | 13 problems | 4/13 verified | Difficulty 1200-3500 | 25m 54s # Problem Rating Tags Accepted Time ✓ A Alphabet City 1300 binary-search, math, strings 3,717 2m 6s ✓ B Battle of Arrays 1400 data-structures, games, greedy 5,659 1m 55s C Cacti Classification 3200 binary-search, constructive-algorithms, interactive 148 1m 51s D Doorway 2000 binary-search, data-structures,...

Codeforces Round 1073 (Div. 1)

Codeforces Round 1073 (Div. 1) Div. 1 | 8 problems | 1/8 verified | Difficulty 1200-3300 | 16m 47s # Problem Rating Tags Accepted Time ✓ A Sorting Game 1200 constructive-algorithms, games, greedy 17,109 1m 53s B1 Sub-RBS (Easy Version) 1400 combinatorics, constructive-algorithms, dp 10,660 3m 3s B2 Sub-RBS (Hard Version) 1900 dp, games, implementation 3,179 3m 32s C Comparable Permutations 2300 greedy, implementation, interactive 1,290 1m 49s D Prufer...

Hello 2026

Hello 2026 Special | 11 problems | 0/11 verified | Difficulty 800-3500 | 23m 31s # Problem Rating Tags Accepted Time ✓ A Binary Array Game 800 games 23,656 1m 37s B Yet Another MEX Problem 1100 constructive-algorithms, greedy 16,159 2m 32s C War Strategy 1500 binary-search, greedy, math 10,658 2m 27s D1 Tree Coloring (Easy Version) 1500 constructive-algorithms, dfs-and-similar, greedy 8,838 2m 31s D2 Tree Coloring (Hard Version) 2100...

Codeforces Round 1077 (Div. 1)

Codeforces Round 1077 (Div. 1) Div. 1 | 8 problems | 0/8 verified | Difficulty 1300-3500 | 15m 1s # Problem Rating Tags Accepted Time ✓ A Restricted Sorting 1300 greedy, sortings 15,850 3m 14s B Shortest Statement Ever 5,276 C Jerry and Tom 2300 data-structures, dfs-and-similar, dsu 1,369 2m 26s D Cool Problem 634 E Doors and Keys 3500 brute-force, data-structures, dp 325 2m 11s F1 Al Fine (Maximizing...

CF 2217F - Interval Game

CF 2217F - Interval Game Rating: 2300 Tags: bitmasks, combinatorics, constructive algorithms, dp, games, greedy, math, probabilities Solve time: 1m 56s Verified: no Solution Problem Understanding The problem describes a two-player turn-based game involving two intervals. Alice chooses the first interval within a fixed bound [1, x1] , and the second interval is picked uniformly at random from all valid intervals in [1, x2] . On a player’s turn, they...

CF 1968D - Permutation Game

CF 1968D - Permutation Game Rating: 1300 Tags: brute force, dfs and similar, games, graphs, greedy, math Solve time: 1m 22s Verified: yes Solution Problem Understanding We are given a directed structure formed by a permutation. From each index $x$, there is exactly one outgoing edge to $p_x$, so the entire system decomposes into disjoint directed cycles, possibly with trees feeding into them, but because $p$ is a permutation, every...

CF 1952E - Sweep Line

CF 1952E - Sweep Line Rating: - Tags: *special, combinatorics, games, math Solve time: 1m 36s Verified: no Solution Problem Understanding We are given a line of positions, each position holding one of three possible values: 0, 1, or 2. The task is to count how many valid global configurations exist that are consistent with the given array, where the notion of “validity” comes from a hidden combinatorial rule involving...

CF 494E - Sharti

CF 494E - Sharti Rating: 3200 Tags: data structures, games Solve time: 1m 19s Verified: yes Solution Problem Understanding We are asked to determine the winner of a two-player combinatorial game played on an $n \times n$ board. The board consists of black and white cells. Initially, only certain rectangles are white, and the rest are black. Players alternate moves, and a move consists of selecting any square of size...

Codeforces Round 1073 (Div. 2)

Codeforces Round 1073 (Div. 2) Type: Div. 2 | Problems: 8 | Verified: 2/8 | Rating range: 800-3200 | Time: 14m 4s Problem Name Rating Tags Solve Time Verified A Array Coloring 800 constructive-algorithms 1m 50s ✓ B MEX Reordering 1000 constructive-algorithms, sortings 1m 8s ✓ C Sorting Game 1200 games 3m 14s ✗ D1 Sub-RBS (Easy Version) 1400 constructive-algorithms 1m 43s ✗ D2 Sub-RBS (Hard Version) 1900 dp, games...

Codeforces Round 942 (Div. 2)

Codeforces Round 942 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 1/7 | Rating range: 800-2800 | Time: 18m 1s Problem Name Rating Tags Solve Time Verified A Contest Proposal 800 brute-force, greedy, two-pointers 2m 28s ✓ B Coin Games 900 games 3m 56s ✗ C Permutation Counting 1400 binary-search, constructive-algorithms, greedy 5m 15s ✗ D1 Reverse Card (Easy Version) 1400 brute-force, math, number-theory 1m 56s ✗ D2...

Codeforces Round 201 (Div. 1)

Codeforces Round 201 (Div. 1) Div. 1 | 5 problems | 3/5 verified | Difficulty 1600-3000 | 6m 17s # Problem Rating Tags Accepted Time ✓ A Alice and Bob 1600 games, math, number-theory 9,347 1m 22s ✓ B Lucky Common Subsequence 2000 dp, strings 4,258 1m 5s ✓ C Number Transformation II 2200 greedy, math 1,506 35s D Robot Control 2600 dp, graphs, shortest-paths 841 1m 50s E Doodle...

MemSQL start[c]up Round 2 - online version

MemSQL start[c]up Round 2 - online version Special | 6 problems | 1/6 verified | Difficulty 1400-3000 | 10m 58s # Problem Rating Tags Accepted Time ✓ A Banana 1400 binary-search, constructive-algorithms, greedy 2,846 2m 1s ✓ B Palindrome 1900 constructive-algorithms, dp 2,373 1m 45s C More Reclamation 2100 games 603 1m 53s D Rectangles and Square 2400 brute-force, dp 350 1m 42s E Counting Skyscrapers 2800 dp, math, probabilities...

CF 346A - Alice and Bob

CF 346A - Alice and Bob Rating: 1600 Tags: games, math, number theory Solve time: 1m 22s Verified: yes Solution Problem Understanding We start with a finite set of distinct positive integers. Two players alternate turns, and on each turn a player is allowed to take any two existing numbers, compute their absolute difference, and insert that value into the set if it is not already present. The set only...

CF 335C - More Reclamation

CF 335C - More Reclamation Rating: 2100 Tags: games Solve time: 1m 53s Verified: no Solution Problem Understanding We are dealing with a two-column grid of arbitrary height r , where each cell initially represents water. Two cities take turns reclaiming cells to turn them into land, but there is a restriction: reclaiming a cell blocks the three neighboring cells in the opposite column from being reclaimed. The goal for...

CF 317D - Game with Powers

CF 317D - Game with Powers Rating: 2300 Tags: dp, games Solve time: 1m 1s Verified: yes Solution Problem Understanding We are given a set of integers from 1 to n. Two players alternate turns, and each move consists of selecting a number that has not been eliminated yet. The twist is in how elimination works: when a player picks a number x, all higher powers of x are also...

CF 277C - Game

CF 277C - Game Rating: 2400 Tags: games, implementation Solve time: 2m 33s Verified: no Solution Problem Understanding Every interior grid line of the paper is divided into unit segments by the lattice points. A cut along a grid line marks all unit segments touched by the knife as already cut. The crucial observation is that the geometry of the paper never changes. Pieces are not moved, and a future...

Codeforces Round 169 (Div. 2)

Codeforces Round 169 (Div. 2) Div. 2 | 5 problems | 4/5 verified | Difficulty 900-2100 | 6m 47s # Problem Rating Tags Accepted Time ✓ A Lunch Rush 900 implementation 30,060 1m 19s ✓ B Little Girl and Game 1300 games, greedy 32,102 1m 39s ✓ C Little Girl and Maximum Sum 1500 data-structures, greedy, implementation 39,517 1m 4s ✓ D Little Girl and Maximum XOR 1700 bitmasks, dp,...

Codeforces Round 170 (Div. 1)

Codeforces Round 170 (Div. 1) Div. 1 | 5 problems | 2/5 verified | Difficulty 1400-2800 | 9m 3s # Problem Rating Tags Accepted Time ✓ A Learning Languages 1400 dfs-and-similar, dsu 21,564 1m 34s ✓ B Set of Points 2300 constructive-algorithms, geometry 847 1m 51s C Game 2400 games, implementation 491 2m 33s D Google Code Jam 2800 dp, probabilities 372 1m 33s E Binary Tree on Plane 2400...

Codeforces Round 167 (Div. 1)

Codeforces Round 167 (Div. 1) Div. 1 | 2 problems | 1/2 verified | Difficulty 2400-2600 | 3m 6s # Problem Rating Tags Accepted Time ✓ D Dima and Figure 2400 dp 478 1m 58s E Dima and Game 2600 dp, games 400 1m 8s ✓

Codeforces Round 173 (Div. 2)

Codeforces Round 173 (Div. 2) Div. 2 | 5 problems | 4/5 verified | Difficulty 800-2200 | 8m 47s # Problem Rating Tags Accepted Time ✓ A Bit++ 800 implementation 358,005 1m 16s ✓ B Painting Eggs 1500 greedy, math 13,971 2m 15s ✓ C XOR and OR 1500 constructive-algorithms, implementation, math 10,178 1m 34s ✓ D Yet Another Number Game 2100 dp, games 1,614 2m 14s E Sausage Maximization...

Croc Champ 2013 - Round 2

Croc Champ 2013 - Round 2 Special | 5 problems | 1/5 verified | Difficulty 1500-2700 | 11m 32s # Problem Rating Tags Accepted Time ✓ A Weird Game 1500 games, greedy 3,195 5m 1s ✓ B Distinct Paths 2700 brute-force, combinatorics 941 2m 30s C Cube Problem 2400 brute-force, math, number-theory 635 2m 37s D Ksusha and Square 2700 geometry, math, probabilities 261 43s E Close Vertices 2700 data-structures,...

CF 293A - Weird Game

CF 293A - Weird Game Rating: 1500 Tags: games, greedy Solve time: 5m 1s Verified: yes Solution Problem Understanding We are asked to analyze a turn-based game between two players, Yaroslav and Andrey, who each have a binary string of length 2·n. They alternately pick positions from the combined index set {1, 2, …, 2·n}. On each turn, the chosen position gives the player the character from their string at...

CF 282D - Yet Another Number Game

CF 282D - Yet Another Number Game Rating: 2100 Tags: dp, games Solve time: 2m 14s Verified: no Solution Problem Understanding We are asked to determine the winner in a turn-based game with a very small sequence of integers, where two players alternate moves. On each turn, a player can either reduce a single element by any positive amount or reduce all elements by the same positive amount. The first...

CF 279E - Beautiful Decomposition

CF 279E - Beautiful Decomposition Rating: 1900 Tags: dp, games, greedy, number theory Solve time: 4m 8s Verified: yes Solution Problem Understanding A beautiful number is any power of two with either sign. In other words, every summand must be one of $$\pm 2^0,\ \pm 2^1,\ \pm 2^2,\dots$$ We are given a positive integer $n$, but not in decimal form. Instead, its binary representation is provided as a string whose...

CF 276B - Little Girl and Game

CF 276B - Little Girl and Game Rating: 1300 Tags: games, greedy Solve time: 1m 39s Verified: yes Solution Problem Understanding We are given a string of lowercase letters and two players who take turns removing a single character. A player wins immediately before their turn if the current letters can be rearranged into a palindrome. Our task is to determine which player will win, assuming both play optimally. The...

CF 273E - Dima and Game

CF 273E - Dima and Game Rating: 2600 Tags: dp, games Solve time: 1m 8s Verified: yes Solution Problem Understanding We are asked to construct sequences of intervals, each interval defined by two integers (l, r), such that the first player has a guaranteed winning strategy in a specific two-player game. Each interval can be split during a move: a player chooses an interval where the difference r - l...

Codeforces Round 159 (Div. 2)

Codeforces Round 159 (Div. 2) Div. 2 | 5 problems | 2/5 verified | Difficulty 1100-2200 | 13m 6s # Problem Rating Tags Accepted Time ✓ A Sockets 1100 greedy, implementation, sortings 6,914 2m 10s ✓ B Playing Cubes 1300 games, greedy, implementation 7,773 2m 28s C View Angle 1800 brute-force, geometry, math 4,719 2m 22s ✓ D Sum 1900 greedy, math 1,719 3m 7s E Greedy Elevator 2200 data-structures,...

CF 257B - Playing Cubes

CF 257B - Playing Cubes Rating: 1300 Tags: games, greedy, implementation Solve time: 2m 28s Verified: no Solution

Codeforces Round 1090 (Div. 4)

Codeforces Round 1090 (Div. 4) Div. 4 | 7 problems | 1/7 verified | Difficulty 800-1800 | 13m 16s # Problem Rating Tags Accepted Time ✓ A The 67th Integer Problem 800 brute-force, games, implementation 34,685 1m 27s ✓ B The 67th 6-7 Integer Problem 800 greedy, math 33,439 1m 49s C The 67th Permutation Problem 800 constructive-algorithms, greedy, math 26,259 2m 4s D The 67th OEIS Problem 1100 constructive-algorithms,...

CF 154D - Flatland Fencing

CF 154D - Flatland Fencing Rating: 2400 Tags: games, math Solve time: 1m 3s Verified: no Solution

CF 2218A - The 67th Integer Problem

CF 2218A - The 67th Integer Problem Rating: 800 Tags: brute force, games, implementation, math Solve time: 1m 27s Verified: yes Solution Problem Understanding The problem asks us to pick an integer $y$ for a given integer $x$ so that the minimum of $x$ and $y$ is as large as possible. We are given multiple test cases, each consisting of a single integer $x$ between -67 and 67. Our output...

Codeforces Round 941 (Div. 1)

Codeforces Round 941 (Div. 1) Div. 1 | 6 problems | 0/6 verified | Difficulty 1400-3300 | 7m 12s # Problem Rating Tags Accepted Time ✓ A Everything Nim 1400 games, greedy, math 16,701 1m 24s B Missing Subsequence Sum 1800 bitmasks, constructive-algorithms, greedy 8,119 1m 17s C Folding Strip 2300 constructive-algorithms, greedy, strings 2,353 1m 8s D Missing Subarray Sum 2900 constructive-algorithms 536 1m 5s E Connected Cubes 3100...

Codeforces Round 934 (Div. 1)

Codeforces Round 934 (Div. 1) Div. 1 | 8 problems | 1/8 verified | Difficulty 1300-3500 | 10m 17s # Problem Rating Tags Accepted Time ✓ A MEX Game 1 1300 games, greedy 21,471 1m 9s ✓ B Non-Palindromic Substring 2000 hashing, implementation, math 4,540 1m 20s C Tree Compass 2300 constructive-algorithms, dfs-and-similar, greedy 2,600 1m 16s D1 Counting Is Fun (Easy Version) 2400 brute-force, combinatorics, dp 1,950 1m 31s...

Codeforces Round 939 (Div. 2)

Codeforces Round 939 (Div. 2) Div. 2 | 7 problems | 3/7 verified | Difficulty 800-3000 | 7m 40s # Problem Rating Tags Accepted Time ✓ A Nene's Game 800 binary-search, brute-force, data-structures 24,189 1m 6s B Nene and the Card Game 800 games, greedy 22,927 53s ✓ C Nene's Magical Matrix 1600 constructive-algorithms, greedy, math 15,142 57s ✓ D Nene and the Mex Operator 2000 bitmasks, brute-force, constructive-algorithms 4,779...

Codeforces Round 934 (Div. 2)

Codeforces Round 934 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 2/7 | Rating range: 800-2800 | Time: 12m 51s Problem Name Rating Tags Solve Time Verified A Destroying Bridges 800 graphs, greedy, math 55s ✓ B Equal XOR 1100 bitmasks, constructive-algorithms 2m 13s ✗ C MEX Game 1 1300 constructive-algorithms, games, greedy 3m 29s ✓ D Non-Palindromic Substring 2000 hashing, implementation, strings 1m 22s ✗ E Tree...

CF 1942E - Farm Game

CF 1942E - Farm Game Rating: 2300 Tags: combinatorics, games Solve time: 1m 56s Verified: yes Solution Problem Understanding The cows of the two farmers must appear in alternating order on the line. Once the order of the first cow is chosen, the entire sequence is fixed: either J N J N ... J N or N J N J ... N J . The actual positions are not fixed....

CF 493D - Vasya and Chess

CF 493D - Vasya and Chess Rating: 1700 Tags: constructive algorithms, games, math Solve time: 1m 25s Verified: yes Solution Problem Understanding We have an $n \times n$ board. The white queen starts at the top-left corner $(1,1)$, and the black queen starts at the top-right corner $(1,n)$. Every other square contains a green pawn. A move is mandatory. On each turn, a player must capture some piece with their...

CF 1956A - Nene's Game

CF 1956A - Nene's Game Rating: 800 Tags: binary search, brute force, data structures, games, greedy Solve time: 1m 6s Verified: no Solution Problem Understanding We are given an increasing list of positions, and a process that repeatedly deletes players from a line. In each round, we look at the current lineup and try to remove the players standing at positions $a_1, a_2, \ldots, a_k$. These positions are always interpreted...

CF 1955F - Unfair Game

CF 1955F - Unfair Game Rating: 1800 Tags: dp, games, greedy, math, schedules Solve time: 1m Verified: no Solution Problem Understanding We are asked to maximize the number of games Bob can win in a repeated XOR game against Alice. The game is played on a multiset of integers containing only ones, twos, threes, and fours. Alice wins if the XOR of all remaining numbers is non-zero; otherwise, Bob wins....

CF 1965A - Everything Nim

CF 1965A - Everything Nim Rating: 1400 Tags: games, greedy, math, sortings Solve time: 1m 24s Verified: no Solution Problem Understanding We are given several independent games, each defined by a list of piles containing stones. Two players alternate turns. A move consists of choosing an integer $k$ that does not exceed the smallest nonempty pile, then simultaneously subtracting $k$ stones from every pile that is still nonempty. Any pile...

CF 1951H - Thanos Snap

CF 1951H - Thanos Snap Rating: 3200 Tags: binary search, dp, games, greedy, trees Solve time: 1m 17s Verified: no Solution Problem Understanding We are given an array whose length is a power of two, and it initially contains all integers from 1 to $2^k$ exactly once. So the array is just a permutation, but its initial order matters. A game is played on this array. A parameter $t$ is...

CF 1956B - Nene and the Card Game

CF 1956B - Nene and the Card Game Rating: 800 Tags: games, greedy Solve time: 53s Verified: yes Solution Problem Understanding We are given a multiset of $2n$ cards, where every number from $1$ to $n$ appears exactly twice in total. These cards are split evenly between two players, you and Nene, so each of you holds $n$ cards. We are only given your hand; Nene’s hand is implicitly determined...

CF 1943A - MEX Game 1

CF 1943A - MEX Game 1 Rating: 1300 Tags: games, greedy Solve time: 1m 9s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game on an array of non-negative integers. Alice begins with an empty array c , and on her turn, she takes any element from the initial array a and appends it to c . Bob, on his turn, removes any element from a...

CF 1965E - Connected Cubes

CF 1965E - Connected Cubes Rating: 3100 Tags: constructive algorithms, games Solve time: 1m 10s Verified: no Solution Problem Understanding We are given an $n \times m$ grid sitting at height $z=1$, where each cell already contains a unit cube with a color. You are allowed to stack additional colored cubes at integer coordinates above this base layer, but you are blocked from using any cell on the coordinate planes...

Codeforces Round 260 (Div. 1)

Codeforces Round 260 (Div. 1) Div. 1 | 5 problems | 5/5 verified | Difficulty 1500-2900 | 7m 50s # Problem Rating Tags Accepted Time ✓ A Boredom 1500 dp 71,930 1m 31s ✓ B A Lot of Games 1900 dfs-and-similar, dp, games 6,839 1m 49s ✓ C Civilization 2100 dfs-and-similar, dp, dsu 6,464 2m 1s ✓ D Serega and Fun 2700 data-structures 3,655 1m 27s ✓ E Function 2900...

CF 455B - A Lot of Games

CF 455B - A Lot of Games Rating: 1900 Tags: dfs and similar, dp, games, implementation, strings, trees Solve time: 1m 49s Verified: yes Solution Problem Understanding The game can be viewed as moving through a trie built from the given strings. We start at the root, which represents the empty string. On each turn a player chooses one outgoing edge, corresponding to appending a character. The current string must...

CF 457F - An easy problem about trees

CF 457F - An easy problem about trees Rating: 3200 Tags: dp, games, greedy, trees Solve time: 4m 23s Verified: no Solution I’m sorry, but I can’t reliably produce a correct full editorial and solution for this 3200-rated problem from the information currently available to me. While I can restate the problem and discuss some observations, I do not have enough confidence in the exact game-theoretic DP needed for Codeforces...

Codeforces Round 206 (Div. 1)

Codeforces Round 206 (Div. 1) Div. 1 | 5 problems | 2/5 verified | Difficulty 1500-2900 | 15m 26s # Problem Rating Tags Accepted Time ✓ A Vasya and Robot 1500 brute-force, greedy, math 5,657 2m 39s ✓ B Game with Strings 2400 bitmasks, dp, games 503 2m 1s C Vasya and Beautiful Arrays 2100 brute-force, dp, number-theory 3,332 2m 47s ✓ D Transferring Pyramid 2900 dp 498 2m 46s...

Codeforces Round 156 (Div. 2)

Codeforces Round 156 (Div. 2) Div. 2 | 5 problems | 5/5 verified | Difficulty 800-2200 | 10m 7s # Problem Rating Tags Accepted Time ✓ A Greg's Workout 800 implementation 31,192 2m 19s ✓ B Code Parsing 1200 implementation 5,459 2m 19s ✓ C Almost Arithmetical Progression 1500 brute-force, dp 5,049 2m 19s ✓ D Mr. Bender and Square 1800 binary-search, implementation, math 2,198 1m 19s ✓ E Furlo...

Codeforces Round 124 (Div. 2)

Codeforces Round 124 (Div. 2) Div. 2 | 2 problems | 2/2 verified | Difficulty 1400-1600 | 2m 55s # Problem Rating Tags Accepted Time ✓ A Plate Game 1600 constructive-algorithms, games, math 6,844 1m 22s ✓ B Limit 1400 math 4,917 1m 33s ✓

Codeforces Round 114 (Div. 1)

Codeforces Round 114 (Div. 1) Div. 1 | 5 problems | 3/5 verified | Difficulty 1600-3000 | 10m 57s # Problem Rating Tags Accepted Time ✓ A Wizards and Trolleybuses 1600 implementation, math 2,184 1m 40s ✓ B Wizards and Huge Prize 1800 dp, math, probabilities 2,450 1m 38s C Wizards and Numbers 2300 games, math 740 1m 39s D Wizards and Roads 3000 data-structures, divide-and-conquer, graph-matchings 217 2m 8s...

Codeforces Round 105 (Div. 2)

Codeforces Round 105 (Div. 2) Div. 2 | 5 problems | 3/5 verified | Difficulty 800-1900 | 9m 21s # Problem Rating Tags Accepted Time ✓ A Insomnia cure 800 constructive-algorithms, implementation, math 112,352 1m 34s B Escape 1500 implementation, math 6,014 1m 12s ✓ C Terse princess 1700 constructive-algorithms, greedy 3,381 2m 14s D Bag of mice 1800 dp, games, math 8,901 1m 55s ✓ E Porcelain 1900 dp...

Codeforces Round 107 (Div. 1)

Codeforces Round 107 (Div. 1) Div. 1 | 5 problems | 4/5 verified | Difficulty 1400-3000 | 11m 8s # Problem Rating Tags Accepted Time ✓ A Win or Freeze 1400 games, math, number-theory 8,591 2m 2s B Quantity of Strings 1600 combinatorics, dfs-and-similar, graphs 5,314 1m 40s ✓ C Smart Cheater 2200 data-structures, math, probabilities 746 2m 11s ✓ D Mission Impassable 2600 dp, strings 738 2m 26s ✓...

CF 150A - Win or Freeze

CF 150A - Win or Freeze Rating: 1400 Tags: games, math, number theory Solve time: 2m 2s Verified: no Solution Problem Understanding We start with a number q written on paper. On each turn, a player must replace the current number with one of its non-trivial divisors, meaning a divisor strictly between 1 and the number itself. If a player cannot make a move, that player wins immediately. This is...

CF 138D - World of Darkraft

CF 138D - World of Darkraft Rating: 2500 Tags: dp, games Solve time: 2m 6s Verified: yes Solution Problem Understanding We have a rectangular board where every cell contains one of three symbols. A move selects an active cell and disables cells along diagonals passing through it. The exact diagonals depend on the symbol. A cell marked L attacks the two diagonals with constant i + j . A cell...

CF 354B - Game with Strings

CF 354B - Game with Strings Rating: 2400 Tags: bitmasks, dp, games Solve time: 2m 1s Verified: no Solution Problem Understanding We are given an $n \times n$ grid of lowercase letters. A valid string is formed by walking from the top-left cell to any reachable cell by moving only right or down, always starting at $(1,1)$. Every move appends the character of the new cell, so each valid string...

CF 142D - Help Shrek and Donkey 2

CF 142D - Help Shrek and Donkey 2 Rating: 2600 Tags: games Solve time: 2m 34s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game on a rectangular grid where each cell may contain a toy soldier from Shrek (green) or Donkey (red), or be empty. The grid has dimensions n × m , and on each row there are at most two soldiers. Players take...

CF 148D - Bag of mice

CF 148D - Bag of mice Rating: 1800 Tags: dp, games, math, probabilities Solve time: 1m 55s Verified: yes Solution Problem Understanding We have a bag containing white and black mice. The princess moves first, then the dragon, then the princess again, and so on. Whoever draws a white mouse immediately wins. If someone draws a black mouse, the game continues. There is one extra rule during the dragon’s turn....

CF 167C - Wizards and Numbers

CF 167C - Wizards and Numbers Rating: 2300 Tags: games, math Solve time: 1m 39s Verified: no Solution Problem Understanding We have a two-player game played with two numbers on a blackboard, call them a and b . Each player can, on their turn, either replace the larger number with the remainder of dividing it by the smaller number, or subtract a positive multiple of the smaller number from the...

CF 255E - Furlo and Rublo and Game

CF 255E - Furlo and Rublo and Game Rating: 2200 Tags: games, implementation, math Solve time: 1m 51s Verified: yes Solution Problem Understanding We have several independent piles of coins. A move picks one pile with size x and replaces it with some smaller value y such that $$x^{1/4} \le y \le x^{1/2}$$ and y < x . The player who cannot make a move loses. Since moves affect only...

CF 197A - Plate Game

CF 197A - Plate Game Rating: 1600 Tags: constructive algorithms, games, math Solve time: 1m 22s Verified: yes Solution Problem Understanding We have a rectangular table with dimensions a × b and an unlimited supply of identical circular plates with radius r . Two players alternate placing plates on the table. Every plate must lie completely inside the rectangle, and plates may touch but cannot overlap. The game ends when...

CF 305E - Playing with String

CF 305E - Playing with String Rating: 2300 Tags: games Solve time: 1m 47s Verified: yes Solution Problem Understanding We are asked to analyze a two-player string game. Players alternate moves. On a turn, a player can select any string fragment available (initially the whole string) and cut a character that is the center of a palindrome of odd length. After cutting, the string splits into three parts: the single...

School Regional Team Contest, Saratov, 2011

School Regional Team Contest, Saratov, 2011 Special | 10 problems | 8/10 verified | Difficulty 1000-2200 | 16m 31s # Problem Rating Tags Accepted Time ✓ A Elevator 1000 brute-force, implementation, math 5,663 1m 26s ✓ B Quiz League 1100 implementation 3,668 1m 21s ✓ C Winnie-the-Pooh and honey 1100 implementation, math 3,947 1m 39s ✓ D Three Sons 1400 brute-force 2,101 1m 35s ✓ E Put Knight! 1400 games,...

Codeforces Beta Round 70 (Div. 2)

Codeforces Beta Round 70 (Div. 2) Div. 2 | 5 problems | 4/5 verified | Difficulty 800-2300 | 12m 16s # Problem Rating Tags Accepted Time ✓ A Haiku 800 implementation, strings 15,434 3m 30s ✓ B Easter Eggs 1200 constructive-algorithms, implementation 15,344 1m 59s C Beaver Game 2000 dp, games, number-theory 2,174 2m 6s ✓ D Archer's Shot 2300 binary-search, geometry, math 373 2m 7s ✓ E Evacuation 2300...

Codeforces Beta Round 73 (Div. 1 Only)

Codeforces Beta Round 73 (Div. 1 Only) Div. 1 | 5 problems | 5/5 verified | Difficulty 1500-2600 | 9m 48s # Problem Rating Tags Accepted Time ✓ A Trains 1500 implementation, math 5,814 1m 15s ✓ B Vasya and Types 1800 implementation, strings 1,265 1m 56s ✓ C Interesting Game 2000 dp, games, math 1,687 1m 9s ✓ D Beautiful Road 2300 dfs-and-similar, dp, dsu 1,055 2m 12s ✓...

Codeforces Beta Round 63 (Div. 2)

Codeforces Beta Round 63 (Div. 2) Div. 2 | 5 problems | 5/5 verified | Difficulty 1000-2000 | 9m 17s # Problem Rating Tags Accepted Time ✓ A Young Physicist 1000 implementation, math 202,257 1m 43s ✓ B Bets 1200 greedy, implementation 3,619 2m 1s ✓ C Game 2000 implementation 674 2m 15s ✓ D Dot 1900 dp, games 1,129 1m 56s ✓ E Subsegments 1800 data-structures, implementation 5,086 1m...

Codeforces Beta Round 68

Codeforces Beta Round 68 Beta | 5 problems | 4/5 verified | Difficulty 1000-2800 | 22m 53s # Problem Rating Tags Accepted Time ✓ A Room Leader 1000 implementation 5,865 1m 35s ✓ B Train 1500 dp, games, greedy 1,785 2m 11s ✓ C Chessboard Billiard 2100 dfs-and-similar, dsu, graphs 1,412 1m 36s ✓ D Hanger 2400 data-structures 413 1m 7s ✓ E Shift It! 2800 constructive-algorithms 185 16m 24s

Codeforces Beta Round 51

Codeforces Beta Round 51 Beta | 5 problems | 3/5 verified | Difficulty 1200-2500 | 10m 12s # Problem Rating Tags Accepted Time ✓ A Flea travel 1200 implementation, math 3,885 1m 24s ✓ B Smallest number 1600 brute-force 3,446 1m 47s ✓ C Pie or die 1900 games 1,828 1m 43s ✓ D Beautiful numbers 2500 dp, number-theory 4,620 3m 29s E Very simple problem 2500 geometry, two-pointers 820...

School Team Contest 1 (Winter Computer School 2010/11)

School Team Contest 1 (Winter Computer School 2010/11) Special | 11 problems | 9/11 verified | Difficulty 1100-2600 | 23m 20s # Problem Rating Tags Accepted Time ✓ A C*++ Calculations 2000 expression-parsing, greedy 794 2m 42s ✓ B Company Income Growth 1300 greedy 3,097 3m 27s ✓ C Moon Craters 2100 dp, sortings 697 4m 25s D Cubical Planet 1100 math 4,664 1m 27s ✓ E What Has Dirichlet...

School Personal Contest #1 (Winter Computer School 2010/11) - Codeforces Beta Round 38 (ACM-ICPC Rules)

School Personal Contest #1 (Winter Computer School 2010/11) - Codeforces Beta Round 38 (ACM-ICPC Rules) Beta | 8 problems | 5/8 verified | Difficulty 800-2400 | 13m 48s # Problem Rating Tags Accepted Time ✓ A Army 800 implementation 26,467 1m 18s ✓ B Chess 1200 brute-force, implementation, math 4,030 2m C Blinds 1400 brute-force 2,561 1m 7s ✓ D Vasya the Architect 1900 implementation 1,075 1m 38s ✓ E...

Codeforces Beta Round 36

Codeforces Beta Round 36 Beta | 5 problems | 2/5 verified | Difficulty 1300-2600 | 9m 36s # Problem Rating Tags Accepted Time ✓ A Extra-terrestrial Intelligence 1300 implementation 3,547 1m 21s ✓ B Fractal 1600 implementation 2,034 1m 52s ✓ C Bowls 2200 geometry, implementation 380 2m 5s D New Game with a Chess Piece 2300 games 769 1m 43s E Two Paths 2600 constructive-algorithms, dsu, graphs 614 2m...

Codeforces Beta Round 15

Codeforces Beta Round 15 Beta | 5 problems | 5/5 verified | Difficulty 1200-2600 | 11m 13s # Problem Rating Tags Accepted Time ✓ A Cottage Village 1200 implementation, sortings 4,495 2m 21s ✓ B Laser 1800 math 1,680 2m 54s ✓ C Industrial Nim 2000 games 2,837 2m 25s ✓ D Map 2500 data-structures, implementation, sortings 913 2m 12s ✓ E Triangles 2600 combinatorics, dp 673 1m 21s ✓

Codeforces Beta Round 3

Codeforces Beta Round 3 Beta | 4 problems | 4/4 verified | Difficulty 1000-2600 | 14m 42s # Problem Rating Tags Accepted Time ✓ A Shortest path of the king 1000 greedy, shortest-paths 22,136 4m 37s ✓ B Lorry 1900 greedy, sortings 5,230 4m 5s ✓ C Tic-tac-toe 1800 brute-force, games, implementation 8,276 4m 37s ✓ D Least Cost Bracket Sequence 2600 greedy 3,945 1m 23s ✓

CF 3C - Tic-tac-toe

CF 3C - Tic-tac-toe Rating: 1800 Tags: brute force, games, implementation Solve time: 4m 37s Verified: yes Problem Understanding We are given a snapshot of a tic-tac-toe board, represented as a 3×3 grid. Each cell is either empty ( . ), contains a cross ( X ), or contains a nought ( 0 ). The first player always places crosses, and the second player places noughts. The board might be...

CF 87C - Interesting Game

CF 87C - Interesting Game Rating: 2000 Tags: dp, games, math Solve time: 1m 9s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game with a single pile of n stones. The players alternate turns, starting with Serozha. On each turn, a player selects one existing pile and splits it into at least two piles that form a strictly decreasing sequence with consecutive differences equal to...

CF 135C - Zero-One

CF 135C - Zero-One Rating: 1900 Tags: constructive algorithms, games, greedy Solve time: 1m 50s Verified: yes Solution Problem Understanding We are given a string consisting of 0 , 1 , and ? . Each character represents a card in a row. During the game, players alternately remove one card until only two cards remain. Masha moves first and wants the final two-bit binary number to be as small as...

CF 120E - Put Knight!

CF 120E - Put Knight! Rating: 1400 Tags: games, math Solve time: 1m 56s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game on an n × n chessboard. Petya and Gena take turns placing knights such that no knight can threaten another. A knight threatens positions in its standard L-shaped moves. The first player unable to place a knight loses, and Petya always starts. The...

CF 74B - Train

CF 74B - Train Rating: 1500 Tags: dp, games, greedy Solve time: 2m 11s Verified: yes Solution Problem Understanding The train has n wagons arranged in a line. The controller moves deterministically: every minute he walks one wagon in his current direction, and when he reaches either end he reverses direction. His path is completely fixed once we know the initial wagon and direction. The stowaway behaves differently depending on...

CF 63E - Sweets Game

CF 63E - Sweets Game Rating: 2000 Tags: bitmasks, dfs and similar, dp, games, implementation Solve time: 2m 13s Verified: yes Solution Problem Understanding The board is a fixed hexagon with 19 cells. Some cells contain chocolates, some are empty. Two players alternate moves, and a move consists of choosing a contiguous segment of chocolates that lies on a straight line parallel to one of the three hexagon directions. Every...

CF 36D - New Game with a Chess Piece

CF 36D - New Game with a Chess Piece Rating: 2300 Tags: games Solve time: 1m 43s Verified: no Solution Problem Understanding We are asked to analyze a two-player game on an $n \times m$ rectangular board. The players take turns moving a single chess piece starting in the top-left corner. On each turn, a player can move the piece one cell right, one cell down, or diagonally $k$ cells...

CF 48E - Ivan the Fool VS Gorynych the Dragon

CF 48E - Ivan the Fool VS Gorynych the Dragon Rating: 2100 Tags: dp, games, graphs Solve time: 2m 21s Verified: yes Solution Problem Understanding The game state is completely described by two numbers: how many heads and how many tails the dragon currently has. From a state (h, t) Ivan may choose one of two move types. If he cuts i heads, where 1 ≤ i ≤ n and...

CF 15C - Industrial Nim

CF 15C - Industrial Nim Rating: 2000 Tags: games Solve time: 2m 25s Verified: yes Solution Problem Understanding Each quarry contributes a consecutive range of heap sizes to a standard Nim game. If a quarry gives us values (x, m) , then its dumpers contain: $$x,\ x+1,\ x+2,\ \dots,\ x+m-1$$ All dumpers from all quarries together form one large Nim position. Since ordinary Nim is played, the winner depends only...

CF 39E - What Has Dirichlet Got to Do with That?

CF 39E - What Has Dirichlet Got to Do with That? Rating: 2000 Tags: dp, games Solve time: 1m 57s Verified: yes Solution Problem Understanding We start with a distinct boxes and b distinct items. Since boxes may stay empty and every item independently chooses one of the boxes, the number of possible placements is simply: $a^b$ Two players alternate turns. On each turn, a player may either increase the...

CF 69D - Dot

CF 69D - Dot Rating: 1900 Tags: dp, games Solve time: 1m 56s Verified: yes Solution Problem Understanding We start with a point on the plane at coordinates (x, y) . Players alternate turns, and on each turn they may do one of two things. They may add one of the given movement vectors to the current position. Every vector has non-negative coordinates, so every normal move pushes the point...

CF 38F - Smart Boy

CF 38F - Smart Boy Rating: 2100 Tags: dp, games, strings Solve time: 2m 49s Verified: no Solution Problem Understanding We start with an empty string. The first player picks any single letter that appears somewhere inside at least one dictionary word. After that, players alternately extend the current string by adding exactly one character either to the front or to the back. The restriction is the core of the...

CF 98E - Help Shrek and Donkey

CF 98E - Help Shrek and Donkey Rating: 2700 Tags: dp, games, math, probabilities Solve time: 2m 25s Verified: yes Solution Problem Understanding There are m + n + 1 distinct cards in total. Shrek initially knows his own m cards, Donkey knows his own n cards, and one card is hidden on the table. Nobody knows the hidden card directly. Players alternate turns, with Shrek moving first. On each...

CF 78C - Beaver Game

CF 78C - Beaver Game Rating: 2000 Tags: dp, games, number theory Solve time: 2m 6s Verified: yes Solution Problem Understanding We have n independent logs, each with length m . On a move, a player chooses one existing log and splits it into several equal pieces. If a log of length x is split into t equal parts, then t > 1 , t must divide x , and...

CF 55C - Pie or die

CF 55C - Pie or die Rating: 1900 Tags: games Solve time: 1m 43s Verified: yes Solution Problem Understanding We have an $n \times m$ grid. Some cells contain pies, and several pies may share the same cell. Each turn has two phases. First, Volodya chooses one pie and moves it by one cell in one of the four directions. If the pie is already on the boundary, he may...