Codeforces Global Round 8

7 problems from Codeforces Global Round 8 (contest 1368), difficulty 800-3500. 4/7 solutions verified against sample I/O.

7 items

Codeforces Global Round 8

Global | 7 problems | 4/7 verified | Difficulty 800-3500 | 27m 28s

#	Problem	Rating	Tags	Accepted	Time	✓
A	C+=	800	brute-force, greedy, implementation	46,235	1m 50s	✓
B	Codeforces Subsequences	1500	brute-force, constructive-algorithms, greedy	21,387	1m 46s	✓
C	Even Picture	1500	constructive-algorithms	14,031	4m 18s
E	Ski Accidents	2500	constructive-algorithms, graphs, greedy	2,363	10m 31s
F	Lamps on a Circle	2600	games, implementation, interactive	1,105	2m 16s	✓
H1	Breadboard Capacity (easy version)	3300	dp, flows, greedy	456	2m	✓
H2	Breadboard Capacity (hard version)	3500		281	4m 47s

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CF 1368H2 - Breadboard Capacity (hard version)

The structure we are working with is a rectangular grid where every cell is a junction and every boundary cell has a port attached to one of the two external systems. Each port is either red or blue.

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CF 1368C - Even Picture

We are asked to construct a set of grid cells on an infinite checkerboard, where each chosen cell is considered “gray”. The shape we build must behave like a graph: cells are vertices, and edges connect cells that share a side. The construction must satisfy three conditions.

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CF 1368F - Lamps on a Circle

We are playing an interactive game on a circular array of n positions. All positions start empty. On each turn, the player is allowed to pick a number k and activate any k positions.

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CF 1368E - Ski Accidents

We are working with a directed acyclic structure where each vertex represents a station on a mountain ski resort and every edge represents a one-way ski track that always goes downhill.

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CF 1368H1 - Breadboard Capacity (easy version)

We have a rectangular breadboard with n rows and m columns of internal nodes. Along the four sides of the board there are ports. The left and right sides contribute n ports each, while the top and bottom sides contribute m ports each. Every port is colored either red or blue.

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CF 1368A - C+=

We start with two positive integers, a and b. In one operation we may add one variable into the other: a += b or b += a. Only one value changes per operation. Our goal is to make at least one of the two numbers become strictly larger than a given limit n.

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CF 1368B - Codeforces Subsequences

The task is to construct a string using only lowercase English letters such that the string contains at least k subsequences that spell out the word "codeforces". A subsequence is formed by selecting characters from the string in order without rearranging them.