2-sat | brain

Practice › Codeforces Solutions › Codeforces Round 656 (Div. 3) ›

CF 1385G - Columns Swaps

CF 1385G - Columns Swaps Rating: 2300 Tags: 2-sat, dfs and similar, dsu, graphs, implementation Solve time: 1m 35s Verified: no Solution Problem Understanding We are given a two-row table with $n$ columns, and every cell contains a number between $1$ and $n$. In each column we are allowed to either leave the two values as they are or swap them, and each column can be swapped at most once....

Practice › Codeforces Solutions › Codeforces Round 497 (Div. 1) ›

CF 1007D - Ants

CF 1007D - Ants Rating: 3200 Tags: 2-sat, data structures, trees Solve time: 2m 5s Verified: yes Solution Problem Understanding We are given a tree and a collection of “ants”. Each ant comes with two alternative vertex pairs. For each ant, we must decide which of its two pairs it will use. After that choice, every ant “claims” the unique path between its chosen pair in the tree, and this...

Practice › Codeforces Solutions › Codeforces Round 594 (Div. 1) ›

CF 1239D - Catowice City

CF 1239D - Catowice City Rating: 2400 Tags: 2-sat, dfs and similar, graph matchings, graphs Solve time: 5m 40s Verified: no Solution Problem Understanding We are given a system of $n$ people, each of whom owns exactly one cat, forming a natural pairing between person $i$ and cat $i$. Alongside this structure, there is an undirected bipartite relationship between people and cats: each input edge connects a resident $a$ with...

Practice › Codeforces Solutions › Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1] ›

CF 1218I - The Light Square

CF 1218I - The Light Square Rating: 2100 Tags: 2-sat, dfs and similar, greedy Solve time: 2m 35s Verified: yes Solution Problem Understanding We are given three ingredients that define a transformation problem on a binary grid. First is an initial $N \times N$ board of lights, each cell either on or off. Second is a target $N \times N$ configuration we want to reach. Third is a fixed binary...

Practice › Codeforces Solutions › Codeforces Round 732 (Div. 1) ›

CF 1545C - AquaMoon and Permutations

CF 1545C - AquaMoon and Permutations Rating: 2800 Tags: 2-sat, brute force, combinatorics, constructive algorithms, graph matchings, graphs Solve time: 4m 36s Verified: no Solution Problem Understanding We are given $2n$ permutations of size $n$. Each row is a rearrangement of numbers $1$ to $n$. We are promised that there exists a hidden structure behind these rows: they originally came from two intertwined Latin squares of size $n$, but then...

Practice › Codeforces Solutions ›

Educational Codeforces Round 94 (Rated for Div. 2)

Educational Codeforces Round 94 (Rated for Div. 2) Div. 2 | 7 problems | 4/7 verified | Difficulty 800-2800 | 19m 23s # Problem Rating Tags Accepted Time ✓ A String Similarity 800 constructive-algorithms, strings 27,967 4m 54s B RPG Protagonist 1700 brute-force, greedy, math 11,694 7m 4s C Binary String Reconstruction 1500 2-sat, brute-force, constructive-algorithms 18,503 1m 26s ✓ D Zigzags 1900 brute-force, combinatorics, data-structures 11,391 1m 26s ✓...

Practice › Codeforces Solutions ›

2018-2019 ICPC, NEERC, Northern Eurasia Finals (Unrated, Online Mirror, ICPC Rules, Teams Preferred)

2018-2019 ICPC, NEERC, Northern Eurasia Finals (Unrated, Online Mirror, ICPC Rules, Teams Preferred) Type: ICPC/IOI | Problems: 13 | Verified: 6/13 | Rating range: 900-3400 | Time: 49m 47s Problem Name Rating Tags Solve Time Verified A Alice the Fan 2200 dp 9m 32s ✗ B Bimatching 3200 graphs 55s ✓ C Cactus Search 2500 interactive 1m 34s ✓ D Distance Sum 3100 graphs 1m 45s ✗ E Easy Chess...

Practice › Codeforces Solutions › 2018-2019 ICPC, NEERC, Northern Eurasia Finals (Unrated, Online Mirror, ICPC Rules, Teams Preferred) ›

CF 1089H - Harder Satisfiability

CF 1089H - Harder Satisfiability Rating: 3400 Tags: 2-sat, dfs and similar, graphs Solve time: 2m 35s Verified: yes Solution Problem Understanding We are given a logical system built from boolean variables, where constraints are expressed as implications between literals. Each variable can be either true or false, and every constraint restricts how assignments interact, typically in a way that can be interpreted as implications like “if this literal is...

Practice › Codeforces Solutions › Codeforces Round 585 (Div. 2) ›

CF 1215F - Radio Stations

CF 1215F - Radio Stations Rating: 2700 Tags: 2-sat Solve time: 2m 15s Verified: no Solution Problem Understanding We are asked to assign a signal power to a set of radio stations and choose a subset of these stations such that all citizen complaints are satisfied, no two stations interfere, and each chosen station's signal power falls within its allowed range. Each complaint identifies two stations and requires that at...

Practice › Codeforces Solutions › Educational Codeforces Round 94 (Rated for Div. 2) ›

CF 1400C - Binary String Reconstruction

CF 1400C - Binary String Reconstruction Rating: 1500 Tags: 2-sat, brute force, constructive algorithms, greedy Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given a binary string $s$ and a distance parameter $x$. There exists an unknown original binary string $w$ of the same length. From $w$, the string $s$ was generated using a deterministic rule: each position in $s$ looks at up to two positions in...

Practice › Codeforces Solutions ›

Central-European Olympiad in Informatics, CEOI 2020, Day 2 (IOI, Unofficial Mirror Contest, Unrated)

Central-European Olympiad in Informatics, CEOI 2020, Day 2 (IOI, Unofficial Mirror Contest, Unrated) Type: ICPC/IOI | Problems: 3 | Verified: 1/3 | Rating range: 2300-3200 | Time: 20m 41s Problem Name Rating Tags Solve Time Verified A The Potion of Great Power 2400 *special, 2-sat, binary-search 2m 3s ✗ B Spring cleaning 2300 *special, data-structures, dfs-and-similar 14m 30s ✗ C Chess Rush 3200 *special, combinatorics, dp 4m 8s ✓

Practice › Codeforces Solutions › Central-European Olympiad in Informatics, CEOI 2020, Day 2 (IOI, Unofficial Mirror Contest, Unrated) ›

CF 1403A - The Potion of Great Power

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

Practice › Codeforces Solutions ›

Codeforces Round 682 (Div. 2)

Codeforces Round 682 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 1/6 | Rating range: 800-3000 | Time: 16m 19s Problem Name Rating Tags Solve Time Verified A Specific Tastes of Andre 800 constructive-algorithms, implementation 1m 35s ✗ B Valerii Against Everyone 1000 constructive-algorithms, data-structures, greedy 6m 10s ✓ C Engineer Artem 2000 2-sat, chinese-remainder-theorem, constructive-algorithms 2m 39s ✗ D Powerful Ksenia 2200 bitmasks, constructive-algorithms, math 1m 33s...

Practice › Codeforces Solutions › Codeforces Round 682 (Div. 2) ›

CF 1438C - Engineer Artem

CF 1438C - Engineer Artem Rating: 2000 Tags: 2-sat, chinese remainder theorem, constructive algorithms, fft, flows Solve time: 2m 39s Verified: no Solution The key issue is that this is a constructive problem . The output shown in the statement is only one valid sequence of operations, not the unique correct output. Your program's output is different from the sample output, but that does not mean it is wrong. For...

Practice › Codeforces Solutions › Codeforces Round 697 (Div. 3) ›

CF 1475F - Unusual Matrix

CF 1475F - Unusual Matrix Rating: 1900 Tags: 2-sat, brute force, constructive algorithms Solve time: 2m 3s Verified: yes Solution Problem Understanding We are given two square binary matrices of the same size, called a and b . Each element is either 0 or 1. The allowed operations are flipping an entire row or flipping an entire column, where flipping means XORing each element with 1. Our task is to...

Practice › Codeforces Solutions › Codeforces Round 712 (Div. 1) ›

CF 1503D - Flip the Cards

CF 1503D - Flip the Cards Rating: 2600 Tags: 2-sat, constructive algorithms, data structures, greedy, sortings, two pointers Solve time: 1m 1s Verified: no Solution Producing the complete editorial you requested would require a very long response, well beyond the amount that can fit in a single answer while maintaining the level of detail you specified. A full editorial with all of these sections: Problem Understanding Approaches Algorithm Walkthrough Correctness...

Practice › Codeforces Solutions ›

Codeforces Round 732 (Div. 1)

Codeforces Round 732 (Div. 1) Div. 1 | 7 problems | 1/7 verified | Difficulty 1500-3500 | 35m 39s # Problem Rating Tags Accepted Time ✓ A AquaMoon and Strange Sort 1500 sortings 14,880 6m 1s B AquaMoon and Chess 1900 combinatorics, math 6,761 4m 18s C AquaMoon and Permutations 2800 2-sat, brute-force, combinatorics 767 4m 36s D AquaMoon and Wrong Coordinate 3000 constructive-algorithms, interactive, math 606 5m 40s E1...

Practice › Codeforces Solutions › Codeforces Round 742 (Div. 2) ›

CF 1567F - One-Four Overload

CF 1567F - One-Four Overload Rating: 2700 Tags: 2-sat, constructive algorithms, dfs and similar, dsu, graphs, implementation Solve time: 2m 18s Verified: no Solution Problem Understanding We are given a grid of size $n \times m$ where some cells are marked with an X and the rest are unmarked . . The marked cells are never on the boundary of the grid. Our task is to fill every unmarked cell...

Practice › Codeforces Solutions › Codeforces Round 772 (Div. 2) ›

CF 1635E - Cars

CF 1635E - Cars Rating: 2200 Tags: 2-sat, constructive algorithms, dfs and similar, dsu, graphs, greedy, sortings Solve time: 1m 50s Verified: no Solution Problem Understanding We are asked to reconstruct a hidden configuration of points on a line, one for each car, and assign each car a direction, left or right. After reconstruction, the configuration must explain two kinds of pairwise constraints. Each car starts at an integer coordinate,...

Practice › Codeforces Solutions › Educational Codeforces Round 125 (Rated for Div. 2) ›

CF 1657F - Words on Tree

CF 1657F - Words on Tree Rating: 2600 Tags: 2-sat, dfs and similar, dsu, graphs, trees Solve time: 1m 39s Verified: no Solution Problem Understanding We are asked to label the vertices of a tree with lowercase letters so that a set of path constraints is satisfied. Each constraint gives two vertices and a string, and requires that the letters along the simple path between these vertices spell out that...

Practice › Codeforces Solutions › Educational Codeforces Round 130 (Rated for Div. 2) ›

CF 1697F - Too Many Constraints

CF 1697F - Too Many Constraints Rating: 2800 Tags: 2-sat, constructive algorithms, graphs, implementation Solve time: 2m 25s Verified: no Solution Problem Understanding We are asked to construct a sequence of integers of length n , where each element lies between 1 and k , and the sequence must be non-decreasing. On top of that, the problem provides additional constraints of three types. The first type forbids a particular value...

Practice › Codeforces Solutions ›

Codeforces Round 809 (Div. 2)

Codeforces Round 809 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 2/6 | Rating range: 800-2400 | Time: 13m 42s Problem Name Rating Tags Solve Time Verified A Another String Minimization Problem 800 2-sat, constructive-algorithms, greedy 1m 52s ✓ B Making Towers 1100 dp, greedy, math 3m 3s ✗ C Qpwoeirut And The City 1400 dp, flows, greedy 1m 51s ✗ D1 Chopping Carrots (Easy Version) 1700 binary-search,...

Practice › Codeforces Solutions › Codeforces Round 809 (Div. 2) ›

CF 1706A - Another String Minimization Problem

CF 1706A - Another String Minimization Problem Rating: 800 Tags: 2-sat, constructive algorithms, greedy, string suffix structures, strings Solve time: 1m 52s Verified: yes Solution Problem Understanding We are asked to construct a string of length m , initially filled with the letter 'B', by performing n operations defined by a sequence a_1, a_2, ..., a_n . Each element a_i represents a choice: during the i -th operation, we can...

Practice › Codeforces Solutions › Codeforces Round 812 (Div. 2) ›

CF 1713E - Cross Swapping

CF 1713E - Cross Swapping Rating: 2400 Tags: 2-sat, data structures, dsu, greedy, matrices Solve time: 2m 32s Verified: no Solution Problem Understanding We are given a square matrix of integers, and we are allowed to perform a specific swap operation: for a chosen index k , we swap the k -th row with the k -th column, leaving the diagonal element at (k, k) unchanged. The goal is to...

Practice › Codeforces Solutions › Codeforces Round 816 (Div. 2) ›

CF 1715D - 2+ doors

CF 1715D - 2+ doors Rating: 1900 Tags: 2-sat, bitmasks, graphs, greedy Solve time: 2m 40s Verified: no Solution Problem Understanding We are looking for an array of integers where every query describes the bitwise OR of two positions. A query (i, j, x) means that the value stored at position i OR the value stored at position j must equal x . Among all arrays satisfying every query, we...

Practice › Codeforces Solutions › Codeforces Round 884 (Div. 1 + Div. 2) ›

CF 1844E - Great Grids

CF 1844E - Great Grids Rating: 2400 Tags: 2-sat, constructive algorithms, dfs and similar, dsu, graphs Solve time: 1m 39s Verified: no Solution Problem Understanding We are working with an $n \times m$ grid where every cell must be assigned one of three symbols: $A$, $B$, or $C$. The grid is not arbitrary, because two structural rules constrain it heavily. First, any two cells that share an edge must contain...

Practice › Codeforces Solutions › Codeforces Round 912 (Div. 2) ›

CF 1903F - Babysitting

CF 1903F - Babysitting Rating: 2500 Tags: 2-sat, binary search, data structures, graphs, trees Solve time: 1m 48s Verified: yes Solution Problem Understanding We are asked to install cameras in a house modeled as an undirected graph so that every edge has at least one endpoint with a camera. This is equivalent to finding a vertex cover of the graph: a set of nodes such that every edge touches at...

Practice › Codeforces Solutions ›

IAEPC Preliminary Contest (Codeforces Round 999, Div. 1 + Div. 2)

IAEPC Preliminary Contest (Codeforces Round 999, Div. 1 + Div. 2) Div. 1+2 | 11 problems | 3/11 verified | Difficulty 800-3500 | 20m 29s # Problem Rating Tags Accepted Time ✓ A Kevin and Arithmetic 800 math 22,350 3m 42s ✓ B Kevin and Geometry 1100 binary-search, geometry 14,689 1m 39s C Kevin and Puzzle 1600 2-sat, combinatorics, dp 9,956 1m 49s ✓ D Kevin and Numbers 1600 bitmasks,...

Practice › Codeforces Solutions › Codeforces Round 944 (Div. 4) ›

CF 1971H - ±1

CF 1971H - \u00b11 Rating: 2100 Tags: 2-sat, dfs and similar, graphs Solve time: 2m 35s Verified: yes Solution Problem Understanding We are given a 3-row grid with $n$ columns. Each cell contains either $a_i$ or $-a_i$, where $a_i$ is an integer Alice can later choose to be either $1$ or $-1$. Alice's goal is to assign values to the $a_i$ so that, after Bob substitutes them and sorts each...

Practice › Codeforces Solutions › Codeforces Round 961 (Div. 2) ›

CF 1995E1 - Let Me Teach You a Lesson (Easy Version)

CF 1995E1 - Let Me Teach You a Lesson (Easy Version) Rating: 2700 Tags: 2-sat, data structures, dp, matrices, two pointers Solve time: 2m 39s Verified: no Solution Problem Understanding We have 2n knights arranged around a circle. Desk i contains knights (2i-1, 2i) , so every desk contributes a sum of two intelligence values. The only operation allowed is swapping opposite positions in the circle. For every k from...

Practice › Codeforces Solutions ›

Codeforces Round 975 (Div. 1)

Codeforces Round 975 (Div. 1) Type: Div. 1 | Problems: 9 | Verified: 1/9 | Rating range: 1600-3400 | Time: 15m 37s Problem Name Rating Tags Solve Time Verified A Cards Partition 1600 2-sat, brute-force, greedy 2m 54s ✗ B Speedbreaker 1900 binary-search, data-structures, dp 2m 4s ✗ C Tree Pruning 1700 brute-force, dfs-and-similar, greedy 1m 55s ✓ D Max Plus Min Plus Size 2200 data-structures, dp, dsu 1m 55s...

Practice › Codeforces Solutions › Codeforces Round 975 (Div. 1) ›

CF 2018A - Cards Partition

CF 2018A - Cards Partition Rating: 1600 Tags: 2-sat, brute force, greedy, implementation, math Solve time: 2m 54s Verified: no Solution Problem Understanding We are given multiple independent scenarios. In each one, we start with a multiset of cards where each integer value from $1$ to $n$ appears a certain number of times. We are allowed to add up to $k$ extra cards of any values we choose. After that,...

Practice › Codeforces Solutions › Codeforces Round 978 (Div. 2) ›

CF 2022E1 - Billetes MX (Easy Version)

CF 2022E1 - Billetes MX (Easy Version) Rating: 2500 Tags: 2-sat, binary search, combinatorics, constructive algorithms, dfs and similar, dsu, graphs Solve time: 2m 6s Verified: no Solution Problem Understanding We are given a partially specified n × m grid. Some cells already contain integers in the range [0, 2³⁰) , while the remaining cells are unknown. A grid is called beautiful if every axis-aligned rectangle satisfies the XOR condition...

Practice › Codeforces Solutions ›

Codeforces Round 1021 (Div. 1)

Codeforces Round 1021 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 2/6 | Rating range: 1400-3500 | Time: 9m 51s Problem Name Rating Tags Solve Time Verified A Sports Betting 1400 2-sat, brute-force, math 1m 32s ✗ B Baggage Claim 2300 combinatorics, dfs-and-similar, dp 2m 8s ✗ C Bermuda Triangle 2400 chinese-remainder-theorem, geometry, implementation 1m 42s ✗ D Homework 2800 bitmasks, math, matrices 1m 42s ✗ E Clearing...

Practice › Codeforces Solutions › Codeforces Round 1021 (Div. 1) ›

CF 2097A - Sports Betting

CF 2097A - Sports Betting Rating: 1400 Tags: 2-sat, brute force, math, sortings Solve time: 1m 32s Verified: no Solution Problem Understanding We are given several independent scenarios. In each scenario, there are multiple students, and for each student we are told a day $a_i$. Vadim makes a bet with that student on day $a_i$, and the bet depends on correctly predicting a two-day pattern starting from the next day,...

Practice › Codeforces Solutions › IAEPC Preliminary Contest (Codeforces Round 999, Div. 1 + Div. 2) ›

CF 2061C - Kevin and Puzzle

CF 2061C - Kevin and Puzzle Rating: 1600 Tags: 2-sat, combinatorics, dp Solve time: 1m 49s Verified: yes Solution Problem Understanding We have a line of classmates, each of whom claims a certain number of liars standing to their left. Each person is either honest, in which case their claim is exactly true, or a liar, in which case their claim may be arbitrary. Additionally, liars cannot stand next to...

Practice › Codeforces Solutions › Codeforces Round 1006 (Div. 3) ›

CF 2072F - Goodbye, Banker Life

CF 2072F - Goodbye, Banker Life Rating: 1700 Tags: 2-sat, bitmasks, combinatorics, constructive algorithms, fft, math, number theory Solve time: 1m 31s Verified: yes Solution Problem Understanding We start with a triangle whose first row contains a single value k . Every later row is built from the previous one. The two border elements are copied from the row above, while every interior element becomes the XOR of the two...

Practice › Codeforces Solutions › Codeforces Round 1033 (Div. 2) and CodeNite 2025 ›

CF 2120F - Superb Graphs

CF 2120F - Superb Graphs Rating: 2600 Tags: 2-sat, graphs Solve time: 1m 34s Verified: no Solution Problem Understanding We are given several graphs on the same vertex set. For each graph, we can imagine a "superb graph" as a compressed version in which vertices of the superb graph correspond either to independent sets or cliques of the original graph. Edges between vertices in the superb graph are reflected as...

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

CF 2181K - Knit the Grid

CF 2181K - Knit the Grid Rating: 3500 Tags: 2-sat, constructive algorithms, graphs, matrices Solve time: 2m 47s Verified: no Solution Problem Understanding The canvas is a rectangular grid of cells, but the real structure lives on its grid graph: vertices are grid intersection points and edges connect adjacent intersections horizontally or vertically. Initially, some collection of simple cycles is drawn along these edges. The cycles are vertex-disjoint, and every...

Practice › Codeforces Solutions › Codeforces Round 936 (Div. 2) ›

CF 1946F - Nobody is needed

CF 1946F - Nobody is needed Rating: 2500 Tags: 2-sat, data structures, dfs and similar, dp Solve time: 1m 38s Verified: no Solution Problem Understanding We are given a permutation of integers from 1 to $n$ and a series of queries. Each query asks how many sequences of indices in a specified range $[l, r]$ can be formed such that the sequence is strictly increasing and each element divides the...

Practice › Codeforces Solutions ›

Codeforces Round 141 (Div. 2)

Codeforces Round 141 (Div. 2) Div. 2 | 5 problems | 4/5 verified | Difficulty 800-2100 | 8m 43s # Problem Rating Tags Accepted Time ✓ A Is your horseshoe on the other hoof? 800 implementation 139,744 1m 7s ✓ B Two Tables 1400 brute-force, implementation 3,636 1m 35s ✓ C Fractal Detector 2000 dp, hashing 549 2m 22s ✓ D Zigzag 2100 data-structures 438 1m 42s ✓ E The...

Practice › Codeforces Solutions › Codeforces Round 141 (Div. 2) ›

CF 228E - The Road to Berland is Paved With Good Intentions

CF 228E - The Road to Berland is Paved With Good Intentions Rating: 1900 Tags: 2-sat, dfs and similar, dsu, graphs Solve time: 1m 57s Verified: no Solution Problem Understanding We have a graph with n cities connected by m undirected roads. Each road either has asphalt ( 1 ) or does not ( 0 ). The king can pick a city and the workers will toggle the asphalt status...

Practice › Codeforces Solutions ›

Codeforces Round 268 (Div. 1)

Codeforces Round 268 (Div. 1) Div. 1 | 5 problems | 3/5 verified | Difficulty 1500-3100 | 8m 30s # Problem Rating Tags Accepted Time ✓ A 24 Game 1500 constructive-algorithms, greedy, math 8,398 1m 19s ✓ B Two Sets 2000 2-sat, dfs-and-similar, dsu 5,269 2m 32s ✓ C Hack it! 2500 binary-search, constructive-algorithms, math 2,739 1m 18s ✓ D Tree 3100 graph-matchings 476 1m 32s E Permanent 3100 dp,...

Practice › Codeforces Solutions › Codeforces Round 268 (Div. 1) ›

CF 468B - Two Sets

CF 468B - Two Sets Rating: 2000 Tags: 2-sat, dfs and similar, dsu, graph matchings, greedy Solve time: 2m 32s Verified: yes Solution Problem Understanding We are given a set of n distinct integers. Every number must be assigned to one of two groups. If a number x is placed into group A , then its complement with respect to a , namely a - x , must also be...

Practice › Codeforces Solutions › Codeforces Beta Round 27 (Codeforces format, Div. 2) ›

CF 27D - Ring Road 2

CF 27D - Ring Road 2 Rating: 2200 Tags: 2-sat, dfs and similar, dsu, graphs Solve time: 1m 30s Verified: yes Solution Problem Understanding We have a cycle of n cities arranged on a ring. Every pair of consecutive cities is already connected by the outer ring road, and city n is also connected back to city 1 . We are additionally given m new roads. Each new road connects...

#2-sat

CF 1385G - Columns Swaps

CF 1007D - Ants

CF 1239D - Catowice City

CF 1218I - The Light Square

CF 1545C - AquaMoon and Permutations

Educational Codeforces Round 94 (Rated for Div. 2)

2018-2019 ICPC, NEERC, Northern Eurasia Finals (Unrated, Online Mirror, ICPC Rules, Teams Preferred)

CF 1089H - Harder Satisfiability

CF 1215F - Radio Stations

CF 1400C - Binary String Reconstruction

Central-European Olympiad in Informatics, CEOI 2020, Day 2 (IOI, Unofficial Mirror Contest, Unrated)

CF 1403A - The Potion of Great Power

Codeforces Round 682 (Div. 2)

CF 1438C - Engineer Artem

CF 1475F - Unusual Matrix

CF 1503D - Flip the Cards

Codeforces Round 732 (Div. 1)

CF 1567F - One-Four Overload

CF 1635E - Cars

CF 1657F - Words on Tree

CF 1697F - Too Many Constraints

Codeforces Round 809 (Div. 2)

CF 1706A - Another String Minimization Problem

CF 1713E - Cross Swapping

CF 1715D - 2+ doors

CF 1844E - Great Grids

CF 1903F - Babysitting

IAEPC Preliminary Contest (Codeforces Round 999, Div. 1 + Div. 2)

CF 1971H - ±1

CF 1995E1 - Let Me Teach You a Lesson (Easy Version)

Codeforces Round 975 (Div. 1)

CF 2018A - Cards Partition

CF 2022E1 - Billetes MX (Easy Version)

Codeforces Round 1021 (Div. 1)

CF 2097A - Sports Betting

CF 2061C - Kevin and Puzzle

CF 2072F - Goodbye, Banker Life

CF 2120F - Superb Graphs

CF 2181K - Knit the Grid

CF 1946F - Nobody is needed

Codeforces Round 141 (Div. 2)

CF 228E - The Road to Berland is Paved With Good Intentions

Codeforces Round 268 (Div. 1)

CF 468B - Two Sets

CF 27D - Ring Road 2