Codeforces Round 868 (Div. 2)

Solutions for Codeforces Round 868 (Div. 2) (contest 1823). 1/6 problems verified against sample I/O. Difficulty range: 800-2600.

6 items

Codeforces Round 868 (Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 1/6 | Rating range: 800-2600 | Time: 10m 33s

Problem Name Rating Tags Solve Time Verified
A A-characteristic 800 combinatorics, constructive-algorithms, math 1m 23s ✗
B Sort with Step 900 brute-force, math, sortings 3m 27s ✗
C Strongly Composite 1300 greedy, math, number-theory 1m 28s ✗
D Unique Palindromes 1900 constructive-algorithms, math, strings 1m 36s ✗
E Removing Graph 2500 brute-force, dp, games 1m 13s ✓
F Random Walk 2600 dp, graphs, math 1m 26s ✗
Practice › Codeforces Solutions › Codeforces Round 868 (Div. 2) ›

CF 1823F - Random Walk

We are given a tree where a chip performs a random walk that stops only when it reaches a designated target vertex $t$.
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Practice › Codeforces Solutions › Codeforces Round 868 (Div. 2) ›

CF 1823B - Sort with Step

I have carefully analyzed the failures. The previous solutions were trying to use “next greater/previous greater element” to compute contributions, but that approach is not the correct algorithm for the Easy Version of Codeforces 1827B1.
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Practice › Codeforces Solutions › Codeforces Round 868 (Div. 2) ›

CF 1823D - Unique Palindromes

We are asked to construct a string of length n such that certain prefixes of the string contain exactly a given number of unique palindromic substrings. Each prefix is defined by a length xi, and the number of unique palindromes it should contain is ci.
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Practice › Codeforces Solutions › Codeforces Round 868 (Div. 2) ›

CF 1823E - Removing Graph

We are asked to determine the winner in a two-player game played on a special type of graph. The graph has each vertex of degree exactly 2, which immediately tells us that every connected component is either a cycle or a simple loop. There are no self-loops or multiple edges.
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Practice › Codeforces Solutions › Codeforces Round 868 (Div. 2) ›

CF 1823C - Strongly Composite

We are given several test cases. In each test case, there is an array of integers, and the total product of all numbers in this array is fixed.
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CF 1823A - A-characteristic

We are asked to construct an array of length $n$ consisting only of 1s and -1s such that the number of pairs of indices $i < j$ with equal elements (both 1 or both -1) is exactly $k$. This number of pairs is referred to as the array's $A$-characteristic.
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