Codeforces Beta Round 86 (Div. 1 Only)

Solutions for Codeforces Beta Round 86 (Div. 1 Only) (contest 113). 5/5 problems verified against sample I/O. Difficulty range: 1600-2700.

5 items

Codeforces Beta Round 86 (Div. 1 Only)

Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1600-2700 | Time: 15m 15s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Grammar Lessons	1600	implementation, strings	4m 41s	✓
B	Petr#	2000	brute-force, data-structures, hashing	3m 20s	✓
C	Double Happiness	2200	brute-force, math, number-theory	3m 20s	✓
D	Museum	2700	math, matrices, probabilities	1m 55s	✓
E	Sleeping	2700	combinatorics, implementation, math	1m 59s	✓

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CF 113A - Grammar Lessons

We are given a single line containing several lowercase words separated by spaces. Every valid word in Petya's language belongs to exactly one grammatical category and exactly one gender, determined entirely by its suffix.

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CF 113B - Petr#

We are asked to count how many distinct substrings of a given string t start with a string sbegin and end with another string send. The key detail is that substrings are considered different only by their content, not by their position in t.

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CF 113C - Double Happiness

We are asked to count the numbers in a given interval $l, r$ that are simultaneously prime and expressible as the sum of two positive squares. In simpler terms, for each number in the interval, we need to check two independent properties.

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CF 113D - Museum

We are asked to model the random movements of two friends inside a museum represented as an undirected connected graph with n rooms and m corridors. Each room has a probability of staying in place for a minute, and otherwise the person moves uniformly to a neighboring room.

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CF 113E - Sleeping

We are asked to count the number of times a digital clock shows a moment where at least k digits change simultaneously while Vasya is watching it. The clock is not necessarily 24-hour or 60-minute - it has h hours and m minutes, where both are arbitrary integers up to 10^9.