Educational Codeforces Round 164 (Rated for Div. 2)

6 problems from Educational Codeforces Round 164 (Rated for Div. 2) (contest 1954), difficulty 900-3100. 2/6 solutions verified against sample I/O.

6 items

Educational Codeforces Round 164 (Rated for Div. 2)

Div. 2 | 6 problems | 2/6 verified | Difficulty 900-3100 | 7m 33s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Painting the Ribbon	900	constructive-algorithms, greedy, math	27,613	1m 3s	✓
B	Make It Ugly	1200	implementation, math	21,508	1m 15s
C	Long Multiplication	1200	greedy, math, number-theory	22,737	1m 13s
D	Colored Balls	1800	combinatorics, dp, math	8,067	1m 43s
E	Chain Reaction	2200	binary-search, data-structures, dsu	2,968	1m 12s
F	Unique Strings	3100	combinatorics, dp, math	359	1m 7s	✓

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CF 1954A - Painting the Ribbon

We are asked to decide whether Alice can paint a ribbon of n parts using m colors such that Bob, who can repaint at most k parts into the same color, cannot make the entire ribbon monochromatic.

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CF 1954B - Make It Ugly

We are given an array of integers that is guaranteed to be "beautiful," which means that through a specific operation, all elements can eventually become the same.

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CF 1954C - Long Multiplication

We are given two very large integers represented as strings, both having the same number of digits. Every digit is between 1 and 9, so there are no zeros to complicate positional effects or leading zero issues.

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CF 1954D - Colored Balls

We are given a collection of balls, each assigned one of n distinct colors, where color i has ai balls. We are allowed to group these balls, but each group can have at most two balls, and no two balls in the same group can have the same color.

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CF 1954E - Chain Reaction

We are given a line of monsters, each with some initial health. One operation consists of choosing a single monster as the starting point of a “chain lightning”.

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CF 1954F - Unique Strings

We are given a binary string of length $n$ where the first $c$ characters are ones and the remaining $n - c$ characters are zeros. We are allowed to perform up to $k$ operations, where each operation flips a zero into a one.