Codeforces Round 893 (Div. 2)

Solutions for Codeforces Round 893 (Div. 2) (contest 1858). 3/6 problems verified against sample I/O. Difficulty range: 800-2600.

6 items

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	✗
E1	Rollbacks (Easy Version)	2500	brute-force, data-structures, dfs-and-similar	1m 23s	✓
E2	Rollbacks (Hard Version)	2600	data-structures, interactive, trees	1m 2s	✓

Practice › Codeforces Solutions › Codeforces Round 893 (Div. 2) ›

CF 1858B - The Walkway

Petya walks past benches numbered from 1 to n. Some benches contain cookie sellers. Whenever Petya reaches a bench, he eats a cookie if one of three things is true: 1. The bench contains a seller, in which case he immediately buys and eats a cookie. 2. He has never eaten before.

Practice › Codeforces Solutions › Codeforces Round 893 (Div. 2) ›

CF 1858D - Trees and Segments

We are given a binary string representing a row of trees, where each position is either an oak or a fir. The quality of a final arrangement depends only on two numbers: the longest consecutive block of zeros and the longest consecutive block of ones.

Practice › Codeforces Solutions › Codeforces Round 893 (Div. 2) ›

CF 1858E2 - Rollbacks (Hard Version)

We are asked to maintain a dynamic array while processing four types of queries: append a number, remove the last $k$ numbers, roll back the last change (append or remove), and report the number of distinct numbers in the array. The array is initially empty.

Practice › Codeforces Solutions › Codeforces Round 893 (Div. 2) ›

CF 1858E1 - Rollbacks (Easy Version)

We are asked to maintain an array under four types of operations: appending an element, removing the last $k$ elements, rolling back the last change (which could be either an append or a removal), and querying the number of distinct elements currently in the array.

Practice › Codeforces Solutions › Codeforces Round 893 (Div. 2) ›

CF 1858C - Yet Another Permutation Problem

We are asked to construct permutations of integers from 1 to $n$ in such a way that, when we compute the greatest common divisor (GCD) between consecutive elements (with wrap-around), the number of distinct GCD values is maximized.

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CF 1858A - Buttons

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.