Codeforces Global Round 20

Solutions for Codeforces Global Round 20 (contest 1672). 4/10 problems verified against sample I/O. Difficulty range: 800-3200.

10 items

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 binary-search, constructive-algorithms, greedy 2m 9s ✗
F1 Array Shuffling 2000 constructive-algorithms, graphs, greedy 1m 53s ✗
F2 Checker for Array Shuffling 2800 constructive-algorithms, dfs-and-similar, graphs 2m 3s ✗
G Cross Xor 3200 constructive-algorithms, graphs, math 1m 33s ✓
H Zigu Zagu 2700 constructive-algorithms, data-structures, greedy 1m 47s ✓
I PermutationForces 3000 data-structures, greedy 52s ✗
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672I - PermutationForces

Codeforces 1672I: PermutationForces
codeforces competitive-programming data-structures greedy Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672H - Zigu Zagu

We are given a binary string and many queries on substrings. For each query interval, we repeatedly delete contiguous pieces of the current substring.
codeforces competitive-programming constructive-algorithms data-structures greedy Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672G - Cross Xor

We are asked to construct a binary grid of size $r times c$ by applying a specific row-column flip operation multiple times starting from an all-zero grid. The operation allows us to pick any cell and flip all values in its row and column using XOR with 1.
codeforces competitive-programming constructive-algorithms graphs math matrices Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672B - I love AAAB

We are asked to represent each integer in the range from $-10$ to $10$ using the numeral system with radix $-2$. In this system, every integer $N$ is written in the form $$N = sum{i=0}^{k} di (-2)^i,$$ where each digit $di in {0,1}$ and the representation is chosen so that the…
codeforces competitive-programming constructive-algorithms implementation Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672F2 - Checker for Array Shuffling

We are given two arrays of the same length. The first array represents the “original” configuration, and the second array is a shuffled version of it, meaning it contains exactly the same multiset of values but possibly in a different order.
codeforces competitive-programming constructive-algorithms dfs-and-similar graphs Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672F1 - Array Shuffling

We are given an array that contains values in the range from 1 to n, possibly with repetitions. Think of this array as a multiset of labeled tokens.
codeforces competitive-programming constructive-algorithms graphs greedy Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672E - notepad.exe

We are dealing with a hidden array of word lengths, and the only way to learn anything about it is by querying a hypothetical text editor.
codeforces competitive-programming binary-search constructive-algorithms greedy interactive Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672D - Cyclic Rotation

We are given two arrays, a and b, of the same length n. The goal is to determine whether we can transform a into b using a specific operation.
codeforces competitive-programming constructive-algorithms greedy implementation two-pointers Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672A - Log Chopping

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.
codeforces competitive-programming games implementation math Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Global Round 20 ›

CF 1672C - Unequal Array

We are given an array of integers and asked to minimize consecutive repetitions. Formally, we define the equality of an array as the number of positions where two consecutive elements are equal.
codeforces competitive-programming constructive-algorithms greedy implementation Jun 10, 2026