Educational Codeforces Round 57 (Rated for Div. 2)

7 problems from Educational Codeforces Round 57 (Rated for Div. 2) (contest 1096), difficulty 800-2500. 4/7 solutions verified against sample I/O.

7 items

Educational Codeforces Round 57 (Rated for Div. 2)

Div. 2 | 7 problems | 4/7 verified | Difficulty 800-2500 | 44m 37s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Find Divisible	800	greedy, implementation, math	19,630	4m 16s
B	Substring Removal	1300	combinatorics, math, strings	11,680	3m 50s
C	Polygon for the Angle	1600	brute-force, geometry	7,239	5m 30s	✓
D	Easy Problem	1800	dp	9,397	6m 4s	✓
E	The Top Scorer	2500	combinatorics, dp, math	1,278	6m 3s	✓
F	Inversion Expectation	2300	dp, math, probabilities	2,060	4m 15s
G	Lucky Tickets	2400	divide-and-conquer, dp, fft	1,965	14m 39s	✓

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CF 1096A - Find Divisible

We are given multiple independent queries, each describing a numeric interval from $l$ to $r$. For each interval, we must pick two different integers inside it such that one of them is a divisor of the other.

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CF 1096F - Inversion Expectation

We are given a sequence of length $n$ that is supposed to be a permutation, except some positions are unknown and marked with $-1$.

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CF 1096B - Substring Removal

We are given a string made of lowercase letters, and we are allowed to remove one contiguous segment from it. After removing that segment, the remaining characters must all be identical, meaning either nothing remains or every remaining character is the same letter.

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CF 1096G - Lucky Tickets

We are building digit strings of fixed even length using a restricted alphabet of digits. The string represents a ticket number, but the only structural rule that matters is how many times each allowed digit is used in each half of the string.

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CF 1096E - The Top Scorer

We are given a final score distribution across $p$ players whose scores are non-negative integers summing to $s$. Hasan is player 1, and his score is only partially constrained: it must be at least $r$, but otherwise unknown.

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CF 1096D - Easy Problem

We are given a string and an integer weight attached to every character position. We are allowed to delete characters, and each deletion costs the weight of the deleted position as it originally appears in the string.

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CF 1096C - Polygon for the Angle

We are working with a regular polygon, meaning all sides and angles are symmetric. The input gives an angle value, and we must decide whether there exists some regular n-gon such that we can pick three vertices $a, b, c$ (not necessarily consecutive) and the angle formed at…