Educational Codeforces Round 55 (Rated for Div. 2)

7 problems from Educational Codeforces Round 55 (Rated for Div. 2) (contest 1082), difficulty 1200-2800. 4/7 solutions verified against sample I/O.

7 items

Educational Codeforces Round 55 (Rated for Div. 2)

Div. 2 | 7 problems | 4/7 verified | Difficulty 1200-2800 | 31m 12s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Vasya and Book	1200	implementation, math	9,273	4m 41s
B	Vova and Trophies	1600	greedy	8,028	4m 31s	✓
C	Multi-Subject Competition	1600	greedy, sortings	6,133	2m 12s	✓
D	Maximum Diameter Graph	1800	constructive-algorithms, graphs, implementation	4,089	6m 31s
E	Increasing Frequency	2000	binary-search, dp, greedy	6,341	4m 54s	✓
F	Speed Dial	2800	dp, strings, trees	532	4m 46s	✓
G	Petya and Graph	2400	flows, graphs	2,697	3m 37s

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CF 1082G - Petya and Graph

We are given a simple undirected graph where each vertex carries a cost and each edge carries a reward. We are allowed to pick any subset of vertices, and then from the edges we may only keep those whose endpoints are both selected.

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CF 1082E - Increasing Frequency

We are given an array where each position stores an integer value. We are allowed to pick exactly one continuous segment and add the same integer value to every element inside that segment. This value can be positive, negative, or zero.

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CF 1082F - Speed Dial

We are given a set of phone numbers, each associated with how frequently Polycarp dials it. Every time a number is dialed, he must physically press digits, but the phone allows up to $k$ special speed dial buttons.

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CF 1082D - Maximum Diameter Graph

We are given a set of vertices, and for each vertex we are told how many edges it is allowed to participate in at most. Our task is to actually construct a simple undirected connected graph that respects these degree limits and, among all such graphs, maximizes the diameter.

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CF 1082A - Vasya and Book

We are given a book with pages arranged in a line from 1 to n. Vasya starts on page x and wants to reach page y. Each button press moves his current page either forward by d pages or backward by d pages, but any move that would leave the interval [1, n] is not allowed.

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CF 1082B - Vova and Trophies

We are given a binary string of length $n$, where each position represents a trophy placed in a row. Each trophy is either golden or silver. The only thing that matters is the structure of contiguous golden segments.

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CF 1082C - Multi-Subject Competition

Each candidate belongs to exactly one subject and brings a numeric contribution, which may be positive or negative.