Codeforces Round 855 (Div. 3)

Solutions for Codeforces Round 855 (Div. 3) (contest 1800). 8/9 problems verified against sample I/O. Difficulty range: 800-2200.

9 items

Codeforces Round 855 (Div. 3)

Type: Div. 3 | Problems: 9 | Verified: 8/9 | Rating range: 800-2200 | Time: 18m 24s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Is It a Cat?	800	implementation, strings	1m 47s	✓
B	Count the Number of Pairs	1000	greedy, strings	2m 57s	✓
C1	Powering the Hero (easy version)	1000	data-structures, greedy	3m 50s	✓
C2	Powering the Hero (hard version)	1100	data-structures, greedy	1m 15s	✓
D	Remove Two Letters	1200	data-structures, greedy, hashing	1m 41s	✓
E1	Unforgivable Curse (easy version)	1400	brute-force, constructive-algorithms, dsu	1m 11s	✓
E2	Unforgivable Curse (hard version)	1500	brute-force, constructive-algorithms, dfs-and-similar	2m 20s	✓
F	Dasha and Nightmares	1900	bitmasks, hashing, meet-in-the-middle	1m 42s	✓
G	Symmetree	2200	dfs-and-similar, hashing, implementation	1m 41s	✗

Practice › Codeforces Solutions › Codeforces Round 855 (Div. 3) ›

CF 1800G - Symmetree

We are given a rooted tree with vertices numbered from 1 to $n$, where vertex 1 is the root. Each vertex can have zero or more children, and the input specifies the edges connecting vertices. The task is to determine whether the tree is symmetrical.

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CF 1800E2 - Unforgivable Curse (hard version)

We have two strings of equal length, s and t. Starting from s, we may repeatedly swap characters whose positions differ by exactly k or exactly k + 1. The question is whether these allowed swaps are powerful enough to transform s into t.

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CF 1800F - Dasha and Nightmares

We are given a list of words and asked to count pairs of words whose concatenation satisfies several strict properties.

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CF 1800D - Remove Two Letters

We are given a string consisting of lowercase Latin letters, and the task is to count how many distinct strings can be formed by removing any two consecutive characters. Each test case consists of a string of length at least three.

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CF 1800E1 - Unforgivable Curse (easy version)

We are given two strings of equal length, and we are allowed to transform the first string into the second by swapping characters, but only under a restricted rule: we can swap positions whose indices differ by either 3 or 4.

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CF 1800C1 - Powering the Hero (easy version)

We process a deck of cards from top to bottom. Positive values represent bonus cards, while 0 represents a hero card. Whenever we encounter a bonus card, we may keep it for later or throw it away.

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CF 1800C2 - Powering the Hero (hard version)

We are given a sequence of cards arranged in a fixed order, and we process them from top to bottom. Each card is either a hero or a bonus. A hero card has value zero and represents an opportunity to finalize one hero in our army.

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CF 1800B - Count the Number of Pairs

Kristina has a string of letters that can be lowercase or uppercase. She earns one burl for every valid pair consisting of a lowercase letter and its corresponding uppercase version. Each letter can only participate in a single pair.

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CF 1800A - Is It a Cat?

We are asked to determine if a given string represents the sound of a cat meowing. The sound must strictly follow the pattern “m-e-o-w” in order, where each letter can appear multiple times consecutively, and both uppercase and lowercase letters are allowed.