Avito Cool Challenge 2018

8 problems from Avito Cool Challenge 2018 (contest 1081), difficulty 800-3500. 5/8 solutions verified against sample I/O.

8 items

Avito Cool Challenge 2018

Special | 8 problems | 5/8 verified | Difficulty 800-3500 | 30m 37s

# Problem Rating Tags Accepted Time ✓
A Definite Game 800 constructive-algorithms, math 13,277 6m ✓
B Farewell Party 1500 constructive-algorithms, implementation 4,668 2m 53s ✓
C Colorful Bricks 1500 combinatorics, dp, math 8,557 5m 19s ✓
D Maximum Distance 1800 dsu, graphs, shortest-paths 4,644 2m 31s ✓
E Missing Numbers 1900 binary-search, constructive-algorithms, greedy 2,820 3m 44s
F Tricky Interactor 2600 constructive-algorithms, implementation, interactive 505 6m 44s
G Mergesort Strikes Back 3200 math, probabilities 433 1m 16s
H Palindromic Magic 3500 data-structures, hashing, strings 131 2m 10s ✓
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CF 1081F - Tricky Interactor

We are given a hidden binary array of length $n$, containing only zeros and ones. We are also told how many ones it originally contains, but not their positions. The array is placed in the hands of an interactive judge that mutates it after every query in a very specific way.
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CF 1081H - Palindromic Magic

We are given two long strings, and from each string we are allowed to pick a single substring that is a palindrome. From the first string we choose one palindromic substring, from the second string we choose another palindromic substring, and we concatenate them in that order.
codeforces competitive-programming data-structures hashing strings Jun 15, 2026
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CF 1081E - Missing Numbers

We are given only half of a hidden sequence of positive integers, specifically every even-positioned value. The full sequence has even length $n$, and has a very rigid structure: if you look at prefix sums, every prefix sum must be a perfect square.
codeforces competitive-programming binary-search constructive-algorithms greedy math number-theory Jun 15, 2026
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CF 1081G - Mergesort Strikes Back

Stopped thinking
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CF 1081A - Definite Game

We are given a single positive integer as the starting value of a number $n$. We are allowed to repeatedly transform this number by choosing an integer $x$ that is strictly smaller than the current value of $n$, with the restriction that $x$ must not divide $n$.
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CF 1081D - Maximum Distance

We are given a connected weighted undirected graph where edges have costs, and a subset of vertices is marked as special.
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CF 1081C - Colorful Bricks

We are painting a line of $n$ bricks, each brick choosing one of $m$ available colors. Once the painting is done, we look at the positions where the color changes compared to the previous brick.
codeforces competitive-programming combinatorics dp math Jun 15, 2026
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CF 1081B - Farewell Party

We are given a group of n people. Each person wore exactly one hat, and every hat belongs to one of n possible types labeled from 1 to n. Multiple people may share the same hat type, and some hat types may not be used at all.
codeforces competitive-programming constructive-algorithms implementation Jun 15, 2026