Codeforces Round 872 (Div. 1)

Solutions for Codeforces Round 872 (Div. 1) (contest 1824). 3/6 problems verified against sample I/O. Difficulty range: 1400-3500.

6 items

Codeforces Round 872 (Div. 1)

Type: Div. 1 | Problems: 6 | Verified: 3/6 | Rating range: 1400-3500 | Time: 11m 28s

Problem Name Rating Tags Solve Time Verified
A LuoTianyi and the Show 1400 greedy, implementation 4m 6s ✗
B1 LuoTianyi and the Floating Islands (Easy Version) 1800 combinatorics, math, probabilities 1m 45s ✓
B2 LuoTianyi and the Floating Islands (Hard Version) 2300 combinatorics, dfs-and-similar, math 1m 19s ✓
C LuoTianyi and XOR-Tree 2500 data-structures, dfs-and-similar, dp 1m 26s ✓
D LuoTianyi and the Function 3000 data-structures 1m 29s ✗
E LuoTianyi and Cartridge 3500 data-structures, trees 1m 23s ✗
Practice › Codeforces Solutions › Codeforces Round 872 (Div. 1) ›

CF 1824E - LuoTianyi and Cartridge

We are given a tree with n vertices, where each vertex has two attributes, ai and bi. Each edge also has two attributes, cj and dj.
codeforces competitive-programming data-structures trees Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 872 (Div. 1) ›

CF 1824A - LuoTianyi and the Show

We have a row of m seats and n people who want to occupy them, each with a fixed type of preference. Some people insist on sitting at a specific numbered seat.
codeforces competitive-programming greedy implementation Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 872 (Div. 1) ›

CF 1824D - LuoTianyi and the Function

We are given an array of integers a of length n, indexed from 1. For any subarray defined by indices i through j, we define a function g(i, j) as the largest integer x such that the set of elements from position i to j is contained in the set of elements from x to j.
codeforces competitive-programming data-structures Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 872 (Div. 1) ›

CF 1824C - LuoTianyi and XOR-Tree

We are given a tree with n vertices, each labeled with a non-negative integer. The root is vertex 1. The goal is to modify as few vertex values as possible so that the XOR of values along every path from the root to any leaf equals zero.
codeforces competitive-programming data-structures dfs-and-similar dp dsu greedy trees Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 872 (Div. 1) ›

CF 1824B1 - LuoTianyi and the Floating Islands (Easy Version)

We are given a tree with $n$ nodes representing islands. On this tree, $k$ distinct nodes are chosen uniformly at random to host people. For any fixed configuration of these $k$ nodes, every island can compute the total distance to all chosen nodes.
codeforces competitive-programming combinatorics math probabilities trees Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 872 (Div. 1) ›

CF 1824B2 - LuoTianyi and the Floating Islands (Hard Version)

We are given a tree with $n$ nodes. Then we choose $k$ distinct nodes uniformly at random, and place one “person” on each of them.
codeforces competitive-programming combinatorics dfs-and-similar math probabilities trees Jun 9, 2026