Codeforces Global Round 18

Solutions for Codeforces Global Round 18 (contest 1615). 4/8 problems verified against sample I/O. Difficulty range: 800-3300.

8 items

Codeforces Global Round 18

Type: Global | Problems: 8 | Verified: 4/8 | Rating range: 800-3300 | Time: 17m 34s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Closing The Gap	800	greedy, math	1m 11s	✓
B	And It's Non-Zero	1300	bitmasks, greedy, math	1m 13s	✓
C	Menorah	1600	brute-force, graphs, greedy	1m 30s	✓
D	X(or)-mas Tree	2200	bitmasks, dfs-and-similar, dsu	3m 26s	✗
E	Purple Crayon	2400	data-structures, dfs-and-similar, games	1m 41s	✗
F	LEGOndary Grandmaster	2800	combinatorics, dp, math	1m 29s	✗
G	Maximum Adjacent Pairs	3300	constructive-algorithms, graph-matchings	1m 46s	✓
H	Reindeer Games	3000	binary-search, constructive-algorithms, data-structures	5m 18s	✗

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CF 1615H - Reindeer Games

Your input: Structure: - t = 4 - Each test case: - one integer n - one line with n integers So format is consistent: Expected: Now observe carefully: [1, 7] → 1 [1, 5, 4] → -1 [12345678, 87654321, 20211218, 23571113] → 4 [1,2,3,4,18,19,5,6,7] → 2 So the output is: not…

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CF 1615G - Maximum Adjacent Pairs

We are given an array with some fixed integers and some positions marked as zero. Each zero must be replaced by any integer from 1 to n, and different zero positions can be filled independently, even with the same value.

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CF 1615D - X(or)-mas Tree

We are given a tree with n nodes and n-1 edges, where each edge can store a non-negative integer representing lights, or -1 if the value is unknown.

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CF 1615F - LEGOndary Grandmaster

We are given a one-dimensional Lego strip of length n, where some positions may or may not contain a Lego block. Our memory of the starting and ending configurations is partial: for each position we either know it has a block (1), we know it is empty (0), or we don't remember (?

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CF 1615E - Purple Crayon

We are given a rooted tree with $n$ nodes, rooted at node 1, where all nodes start white. Two players, Red and Blue, take turns coloring nodes. Red goes first and can color at most $k$ nodes red by choosing entire subtrees.

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CF 1615C - Menorah

We have a row of candles on a Hanukkah menorah, and each candle is either lit or unlit. The current state is given as a binary string a, where 1 indicates a lit candle and 0 indicates unlit. We are asked to reach a target configuration b using a special operation.

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CF 1615B - And It's Non-Zero

We are given many test cases, and each test case describes a contiguous array of integers from $l$ to $r$. The array is not arbitrary, it is always a full interval with no gaps.

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CF 1615A - Closing The Gap

We have a row of towers, each with a certain number of blocks stacked vertically. The goal is to make the heights of all towers as close as possible. On any day, we can take a block from one tower and place it on another tower.