Codeforces Round 836 (Div. 2)

Solutions for Codeforces Round 836 (Div. 2) (contest 1758). 1/6 problems verified against sample I/O. Difficulty range: 800-3000.

6 items

Codeforces Round 836 (Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 1/6 | Rating range: 800-3000 | Time: 31m 38s

Problem Name Rating Tags Solve Time Verified
A SSeeeeiinngg DDoouubbllee 800 constructive-algorithms, strings 2m 37s ✗
B XOR = Average 900 constructive-algorithms 12m 43s ✗
C Almost All Multiples 1400 greedy, number-theory 9m 7s ✗
D Range = \u221aSum 1800 binary-search, brute-force, constructive-algorithms 3m 17s ✗
E Tick, Tock 2500 combinatorics, dfs-and-similar, dsu 2m 34s ✓
F Decent Division 3000 constructive-algorithms, data-structures 1m 20s ✗
Practice › Codeforces Solutions › Codeforces Round 836 (Div. 2) ›

CF 1758B - XOR = Average

We are asked to construct, for each test case, a sequence of integers whose XOR of all elements equals the arithmetic mean of the sequence. In other words, if we combine all numbers using XOR and also compute their sum divided by the length, these two values must match exactly.
codeforces competitive-programming constructive-algorithms Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 836 (Div. 2) ›

CF 1758F - Decent Division

I can't reliably write a complete editorial and accepted solution for Codeforces 1758F from memory alone. This is a highly nontrivial 3000-rated constructive/data-structure problem, and the official editorial text is not available through the sources I can access right now.
codeforces competitive-programming constructive-algorithms data-structures Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 836 (Div. 2) ›

CF 1758C - Almost All Multiples

We need to construct a permutation of the integers from 1 to n with three special requirements. The first position must contain x. The last position must contain 1. For every position i from 1 to n-1, the value placed there must be a multiple of i.
codeforces competitive-programming greedy number-theory Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 836 (Div. 2) ›

CF 1758E - Tick, Tock

We are given an $n times m$ grid where each cell either has a clock showing a number between 0 and $h-1$ or is empty. The allowed moves let us pick a row or column and advance all clocks in that row or column by one hour modulo $h$.
codeforces competitive-programming combinatorics dfs-and-similar dsu graphs Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 836 (Div. 2) ›

CF 1758D - Range = √Sum

We are asked to construct a sequence of distinct integers of length $n$ such that the difference between the maximum and minimum element equals the square root of the sum of all elements.
codeforces competitive-programming binary-search brute-force constructive-algorithms math two-pointers Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 836 (Div. 2) ›

CF 1758A - SSeeeeiinngg DDoouubbllee

We are given a string s. If we "double" the string, every character appears twice. For example, "abc" becomes the multiset of characters in "aabbcc". Our task is not to output the doubled string itself.
codeforces competitive-programming constructive-algorithms strings Jun 9, 2026