Codeforces Round 806 (Div. 4)

Solutions for Codeforces Round 806 (Div. 4) (contest 1703). 3/7 problems verified against sample I/O. Difficulty range: 800-1600.

7 items

Codeforces Round 806 (Div. 4)

Type: Div. 4 | Problems: 7 | Verified: 3/7 | Rating range: 800-1600 | Time: 15m 33s

Problem Name Rating Tags Solve Time Verified
A YES or YES? 800 brute-force, implementation, strings 1m 50s ✓
B ICPC Balloons 800 data-structures, implementation 1m 38s ✓
C Cypher 800 brute-force, implementation, strings 2m 42s ✗
D Double Strings 1100 brute-force, data-structures, strings 1m 31s ✓
E Mirror Grid 1200 implementation 2m 36s ✗
F Yet Another Problem About Pairs Satisfying an Inequality 1300 binary-search, data-structures, dp 2m 41s ✗
G Good Key, Bad Key 1600 bitmasks, brute-force, dp 2m 35s ✗
Practice › Codeforces Solutions › Codeforces Round 806 (Div. 4) ›

CF 1703G - Good Key, Bad Key

We are asked to open a sequence of chests, each containing some number of coins, using either “good” or “bad” keys.
codeforces competitive-programming bitmasks brute-force dp greedy math Jun 9, 2026
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CF 1703F - Yet Another Problem About Pairs Satisfying an Inequality

Two constructions are proposed for generating a random variable $X$ with a nontrivial distribution on $[-1,1]$. The first maps a single uniform deviate through a trigonometric transformation.
codeforces competitive-programming binary-search data-structures dp greedy sortings Jun 9, 2026
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CF 1703E - Mirror Grid

We are given an $n times n$ grid whose cells contain only 0 or 1. We may flip any cell, changing 0 to 1 or 1 to 0, and each flip costs one operation. The goal is to make the grid look identical after rotating it by $90^circ$, $180^circ$, or $270^circ$.
codeforces competitive-programming implementation Jun 9, 2026
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CF 1703D - Double Strings

We are given a collection of short lowercase strings, each with length at most 8. For every string in the list, we need to decide whether it can be formed by taking two strings from the same list and concatenating them in order.
codeforces competitive-programming brute-force data-structures strings Jun 9, 2026
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CF 1703C - Cypher

Two constructions are proposed for generating a random variable $X$ with a nontrivial distribution on $[-1,1]$. The first maps a single uniform deviate through a trigonometric transformation.
codeforces competitive-programming brute-force implementation strings Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 806 (Div. 4) ›

CF 1703A - YES or YES?

We are asked to check whether a three-character string represents the word "YES", ignoring letter case. Each test case provides a single string, and we must output a uniform "YES" or "NO" for each one.
codeforces competitive-programming brute-force implementation strings Jun 9, 2026
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CF 1703B - ICPC Balloons

The contest system processes a sequence of problem solves in time order. Each character in the input string represents a problem label from A to Z, and each occurrence means some team solved that problem at that moment.
codeforces competitive-programming data-structures implementation Jun 9, 2026