Codeforces Round 866 (Div. 1)

Solutions for Codeforces Round 866 (Div. 1) (contest 1819). 0/6 problems verified against sample I/O. Difficulty range: 1300-3500.

6 items

Codeforces Round 866 (Div. 1)

Type: Div. 1 | Problems: 6 | Verified: 0/6 | Rating range: 1300-3500 | Time: 12m 44s

Problem Name Rating Tags Solve Time Verified
A Constructive Problem 1300 brute-force, greedy 4m 56s ✗
B The Butcher 1900 geometry, greedy, implementation 1m 42s ✗
C The Fox and the Complete Tree Traversal 2400 constructive-algorithms, dp, implementation 1m 24s ✗
D Misha and Apples 2800 brute-force, data-structures, dp 1m 40s ✗
E Roads in E City 3200 interactive, math, probabilities 1m 33s ✗
F Willy-nilly, Crack, Into Release! 3500 data-structures, dp 1m 29s ✗
Practice › Codeforces Solutions › Codeforces Round 866 (Div. 1) ›

CF 1819A - Constructive Problem

Now the problem is clearer. The previous “corrected” code only avoided the crash, but the logic was still wrong, producing smaller numbers than expected. That means the core algorithm for computing the output per n is incorrect. Let’s carefully reason through this.
codeforces competitive-programming brute-force greedy Jun 9, 2026
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CF 1819E - Roads in E City

We are given a city represented as a graph with intersections as nodes and roads as edges. Some roads have been repaired and allow traffic, while others have not. Our task is to determine exactly which roads are repaired.
codeforces competitive-programming interactive math probabilities trees Jun 9, 2026
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CF 1819F - Willy-nilly, Crack, Into Release!

We are asked to analyze sequences of operations on strings built from the letters a, b, c, d. Certain unordered pairs, namely ab, bc, cd, and da, are called "good" and allow controlled transformations on the string.
codeforces competitive-programming data-structures dp Jun 9, 2026
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CF 1819C - The Fox and the Complete Tree Traversal

We are given an undirected tree with up to two hundred thousand vertices. The movement rule is unusual: from a vertex, the fox can jump to any vertex within graph distance at most two.
codeforces competitive-programming constructive-algorithms dp implementation math trees Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 866 (Div. 1) ›

CF 1819D - Misha and Apples

In this problem, we have a sequence of apple stalls, each selling a subset of apple types numbered from 1 to $m$. Danya, the buyer, walks through the stalls in order and adds one of each apple type from the current stall into his backpack.
codeforces competitive-programming brute-force data-structures dp two-pointers Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 866 (Div. 1) ›

CF 1819B - The Butcher

We are given a multiset of axis-aligned rectangles. Each rectangle is the result of repeatedly cutting an initial unknown rectangle along integer grid lines.
codeforces competitive-programming geometry greedy implementation sortings two-pointers Jun 9, 2026