Educational Codeforces Round 86 (Rated for Div. 2)

4 problems from Educational Codeforces Round 86 (Rated for Div. 2) (contest 1342), difficulty 1000-3000. 1/4 solutions verified against sample I/O.

4 items

Educational Codeforces Round 86 (Rated for Div. 2)

Div. 2 | 4 problems | 1/4 verified | Difficulty 1000-3000 | 13m 44s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Road To Zero	1000	greedy, math	46,404	2m 20s	✓
B	Binary Period	1100	constructive-algorithms, strings	24,582	3m 32s
C	Yet Another Counting Problem	1600	math, number-theory	14,996	4m 50s
F	Make It Ascending	3000	bitmasks, brute-force, dp	989	3m 2s

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CF 1342C - Yet Another Counting Problem

We are working with integers and modular arithmetic, but the structure becomes clearer if we think of the infinite number line as being colored by a periodic rule. For any integer $x$, we compute two values: first we take $x bmod a$, then reduce that result modulo $b$.

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CF 1342B - Binary Period

We are given a binary string and asked to embed it into a larger binary string while preserving order as a subsequence.

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CF 1342F - Make It Ascending

We are given an array of integers, and we are allowed to repeatedly perform an operation where we pick two distinct indices, add the value from the first index to the second, and remove the first element from the array.

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CF 1342A - Road To Zero

We start with two independent counters, x and y, and want to bring both to zero. We are allowed to modify them in two different ways, each with a cost.