Codeforces Round 770 (Div. 2)

Solutions for Codeforces Round 770 (Div. 2) (contest 1634). 3/6 problems verified against sample I/O. Difficulty range: 800-2700.

6 items

Codeforces Round 770 (Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2700 | Time: 10m

Problem Name Rating Tags Solve Time Verified
A Reverse and Concatenate 800 greedy, strings 1m 25s ✗
B Fortune Telling 1400 bitmasks, math 1m 21s ✓
C OKEA 1000 constructive-algorithms 1m 25s ✓
D Finding Zero 2000 constructive-algorithms, interactive, math 1m 45s ✗
E Fair Share 2400 constructive-algorithms, data-structures, dfs-and-similar 2m 41s ✗
F Fibonacci Additions 2700 brute-force, data-structures, hashing 1m 23s ✓
Practice › Codeforces Solutions › Codeforces Round 770 (Div. 2) ›

CF 1634E - Fair Share

This problem is rated 3500 and its solution relies on a fairly deep structural characterization of graphs whose cycle space admits a consistent cyclic orientation.
codeforces competitive-programming constructive-algorithms data-structures dfs-and-similar graph-matchings graphs Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Round 770 (Div. 2) ›

CF 1634D - Finding Zero

We are given an array of hidden non-negative integers, and exactly one position in it contains a zero. Our only way to learn about the array is through queries that inspect any three distinct indices.
codeforces competitive-programming constructive-algorithms interactive math Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Round 770 (Div. 2) ›

CF 1634F - Fibonacci Additions

We are asked to maintain two integer arrays, A and B, under a sequence of operations called Fibonacci additions. Each operation specifies a segment [l, r] and an array to update.
codeforces competitive-programming brute-force data-structures hashing implementation math Jun 10, 2026
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CF 1634A - Reverse and Concatenate

We are given a string s of length n and a number k. We can perform exactly k operations on s, where each operation is either appending the reverse of the string to itself (s + rev(s)) or prepending the reverse (rev(s) + s).
codeforces competitive-programming greedy strings Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Round 770 (Div. 2) ›

CF 1634C - OKEA

We are asked to arrange $n cdot k$ items, priced from $1$ to $n cdot k$, into a grid with $n$ shelves and $k$ items per shelf. The key restriction is that the mean price of any contiguous segment of items on a shelf must be an integer. Each number must appear exactly once.
codeforces competitive-programming constructive-algorithms Jun 10, 2026
Practice › Codeforces Solutions › Codeforces Round 770 (Div. 2) ›

CF 1634B - Fortune Telling

We are given an array of integers, and a process that runs left to right over this array. A person starts with some initial value and, at each position, must choose one of two actions: add the current array value to their running number, or XOR the current array value with it.
codeforces competitive-programming bitmasks math Jun 10, 2026