Codeforces Round 871 (Div. 4)

Solutions for Codeforces Round 871 (Div. 4) (contest 1829). 6/8 problems verified against sample I/O. Difficulty range: 800-1700.

8 items

Codeforces Round 871 (Div. 4)

Type: Div. 4 | Problems: 8 | Verified: 6/8 | Rating range: 800-1700 | Time: 10m 54s

Problem Name Rating Tags Solve Time Verified
A Love Story 800 implementation, strings 1m ✓
B Blank Space 800 implementation 2m 10s ✗
C Mr. Perfectly Fine 800 bitmasks, greedy, implementation 1m 8s ✓
D Gold Rush 1000 brute-force, dfs-and-similar, dp 1m 23s ✓
E The Lakes 1100 dfs-and-similar, dsu, graphs 1m 20s ✓
F Forever Winter 1300 dfs-and-similar, graphs, math 1m ✓
G Hits Different 1600 data-structures, dp, implementation 1m 49s ✗
H Don't Blame Me 1700 bitmasks, combinatorics, dp 1m 4s ✓
Practice › Codeforces Solutions › Codeforces Round 871 (Div. 4) ›

CF 1829G - Hits Different

The structure in this problem is a fixed pyramid of numbered cans, where each position in the pyramid contains a square number.
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CF 1829H - Don't Blame Me

We are given an array where every element is a small integer, specifically a 6-bit value. From this array, we can choose any non-empty subsequence, meaning we pick any subset of indices while preserving order, although order does not actually matter for the bitwise operation.
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CF 1829F - Forever Winter

We are given a graph generated by a simple "snowflake" process. There is a central vertex, then $x$ vertices connected directly to the center, and then $y$ vertices connected to each of the $x$ outer vertices.
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CF 1829E - The Lakes

We are given a two-dimensional grid representing terrain, where each cell contains a non-negative integer indicating the depth of water at that location.
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CF 1829D - Gold Rush

We start with a single pile containing n gold nuggets. The only allowed move takes one existing pile and splits it into exactly two smaller piles, with a strict structure: one of the new piles must be exactly twice the size of the other.
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CF 1829B - Blank Space

The solution correctly generalizes the serial test from pairs to $k$-tuples by grouping the sequence into disjoint blocks of length $k$, ensuring independence under the null hypothesis.
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CF 1829C - Mr. Perfectly Fine

Victor has two independent skills he wants to acquire, and each book he can read either teaches him skill 1, skill 2, both, or none. Every book also has a time cost.
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CF 1829A - Love Story

We are given a fixed reference string, “codeforces”, and for each test case we receive another string of the same length, exactly 10 lowercase letters. The task is to compare these two strings position by position and count how many positions contain different characters.
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