Codeforces Global Round 12

Solutions for Codeforces Global Round 12 (contest 1450). 1/10 problems verified against sample I/O. Difficulty range: 800-3500.

10 items

Codeforces Global Round 12

Type: Global | Problems: 10 | Verified: 1/10 | Rating range: 800-3500 | Time: 35m 15s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Avoid Trygub	800	constructive-algorithms, sortings	1m 38s	✗
B	Balls of Steel	1000	brute-force, geometry, greedy	11m 49s	✓
C1	Errich-Tac-Toe (Easy Version)	2100	constructive-algorithms, math	6m 6s	✗
C2	Errich-Tac-Toe (Hard Version)	2300	constructive-algorithms, math	1m 41s	✗
D	Rating Compression	1800	binary-search, data-structures, greedy	1m 50s	✗
E	Capitalism	2700	constructive-algorithms, dfs-and-similar, graphs	1m 59s	✗
F	The Struggling Contestant	2400	constructive-algorithms, greedy	4m 12s	✗
G	Communism	3500	bitmasks, dp, trees	1m 39s	✗
H1	Multithreading (Easy Version)	2900	combinatorics, fft, math	1m 53s	✗
H2	Multithreading (Hard Version)	3300	combinatorics, implementation, math	2m 28s	✗

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CF 1450H2 - Multithreading (Hard Version)

We are given a circle of points, each point representing a spool that must be paired with exactly one other spool using a straight chord. Every spool has a color, black or white, and some positions are initially uncolored and can be assigned either color.

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CF 1450B - Balls of Steel

We are given several steel balls placed at distinct coordinates on a plane. A charged ball acts like a magnet with radius measured in Manhattan distance.

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CF 1450H1 - Multithreading (Easy Version)

We are working with points placed on a circle, where each position can be colored black, white, or left undecided. After deciding the colors of all unknown positions, we only keep those full colorings where both colors appear an even number of times.

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CF 1450F - The Struggling Contestant

We are given several independent test cases. In each one, we have a sequence of problem tags, and we want to arrange all indices of this sequence into a permutation, meaning we reorder which problem we solve at each step. Two constraints shape this ordering.

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CF 1450G - Communism

We are given a row of n workers, each with a job category represented by a lowercase English letter. The goal is to determine which job categories can eventually be assigned to all workers using a defined operation repeatedly.

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CF 1450E - Capitalism

We are given a connected undirected graph where each vertex represents a person and each edge represents a friendship.

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CF 1450C1 - Errich-Tac-Toe (Easy Version)

We are given a square board where each cell may be empty or contain an X. The goal is to modify the board so that no row or column contains three identical non-empty symbols in a consecutive block.

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CF 1450D - Rating Compression

We are given an array of integers representing the rating graph of a user on a competitive programming platform. For each integer $k$ from 1 to $n$, we are asked to consider the "k-compression" of the array.

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CF 1450C2 - Errich-Tac-Toe (Hard Version)

We are given a square board filled with three possible symbols: empty cells, X tokens, and O tokens. The only way a configuration becomes “bad” is when three identical tokens appear consecutively in a straight line, either horizontally or vertically.

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CF 1450A - Avoid Trygub

We are given a string a consisting of lowercase English letters. The task is to reorder its characters into a string b such that the string "trygub" does not appear as a subsequence in b.