Educational Codeforces Round 87 (Rated for Div. 2)

6 problems from Educational Codeforces Round 87 (Rated for Div. 2) (contest 1354), difficulty 900-2600. 5/6 solutions verified against sample I/O.

6 items

Educational Codeforces Round 87 (Rated for Div. 2)

Div. 2 | 6 problems | 5/6 verified | Difficulty 900-2600 | 23m 25s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Alarm Clock	900	math	24,889	4m 38s	✓
B	Ternary String	1200	binary-search, dp, implementation	35,279	1m 47s	✓
C1	Simple Polygon Embedding	1400	binary-search, geometry, math	16,356	4m 38s	✓
C2	Not So Simple Polygon Embedding	2000	binary-search, brute-force, geometry	6,372	5m 12s	✓
D	Multiset	1900	binary-search, data-structures	10,159	1m 41s	✓
G	Find a Gift	2600	binary-search, interactive, probabilities	962	5m 29s

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CF 1354G - Find a Gift

We are given a row of boxes, each box hiding either a valuable gift or a stone. Exactly k boxes contain gifts, and every other box contains stones. The key structural property is about weights.

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CF 1354C2 - Not So Simple Polygon Embedding

We are given a regular polygon with $2n$ vertices, all edges equal to 1. The polygon is convex, and we are allowed to rotate it freely. We must place it inside a square, also freely rotatable, such that every point of the polygon lies inside or on the square boundary.

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CF 1354C1 - Simple Polygon Embedding

We are working with a fixed geometric object: a regular polygon with $2n$ sides, each side having length 1. This polygon is convex and highly symmetric, so its shape is completely determined once we fix how it is oriented and scaled in the plane.

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CF 1354A - Alarm Clock

We are simulating a very simple system that evolves over time in discrete “sleep cycles.” A person needs to accumulate at least a target amount of effective sleep before they are allowed to get out of bed.

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CF 1354D - Multiset

We are maintaining a collection of integers where duplicates are allowed, and the collection changes over time. Initially we are given a sorted list of values that already form the starting multiset. After that, we receive a long sequence of operations.

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CF 1354B - Ternary String

We are given multiple test cases, and each test case is a string made only of the characters 1, 2, and 3. For each string, we need to find the shortest continuous segment (substring) that contains at least one occurrence of each of the three characters.