Codeforces Beta Round 23

Solutions for Codeforces Beta Round 23 (contest 23). 4/5 problems verified against sample I/O. Difficulty range: 1200-2600.

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Codeforces Beta Round 23

Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1200-2600 | Time: 11m 15s

Problem	Name	Rating	Tags	Solve Time	Verified
A	You're Given a String...	1200	brute-force, greedy	1m 55s	✓
B	Party	1600	constructive-algorithms, graphs, math	3m 27s	✓
C	Oranges and Apples	2500	constructive-algorithms, sortings	2m 29s	✓
D	Tetragon	2600	geometry, math	2m 11s	✗
E	Tree	2500	dp	1m 13s	✓

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CF 23A - You're Given a String...

We are given a string of lowercase letters, and the task is to find the length of the longest substring that occurs at least twice in the string. The repeated occurrences may overlap. The input is a single string of at most 100 characters.

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CF 23B - Party

We can think of the party as an undirected friendship graph. Every person is a vertex, and an edge means two people are friends.

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CF 23C - Oranges and Apples

We have 2N - 1 boxes. Every box contains two numbers, the number of apples and the number of oranges inside it. We must choose exactly N boxes such that the chosen set contains at least half of all apples and at least half of all oranges across every box.

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CF 23D - Tetragon

We are given three points in the plane. Each point is the midpoint of one side of an unknown strictly convex quadrilateral, and all four sides of that quadrilateral have equal length.

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CF 23E - Tree

We are given a tree with _n_ nodes, described by _n-1_ edges. A tree is a connected acyclic graph, so there is exactly one path between any two vertices. Bob can delete any subset of edges, possibly none, and then he looks at the sizes of the resulting connected components.