Educational Codeforces Round 67 (Rated for Div. 2)

Solutions for Educational Codeforces Round 67 (Rated for Div. 2) (contest 1187). 3/7 problems verified against sample I/O. Difficulty range: 900-2500.

7 items

Educational Codeforces Round 67 (Rated for Div. 2)

Type: Div. 2 | Problems: 7 | Verified: 3/7 | Rating range: 900-2500 | Time: 46m 59s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Stickers and Toys	900	math	4m 14s	✓
B	Letters Shop	1300	binary-search, implementation, strings	2m 58s	✓
C	Vasya And Array	1800	constructive-algorithms, greedy, implementation	5m 32s	✗
D	Subarray Sorting	2400	data-structures, sortings	12m 26s	✗
E	Tree Painting	2100	dfs-and-similar, dp, trees	8m 22s	✗
F	Expected Square Beauty	2500	dp, math, probabilities	5m 41s	✓
G	Gang Up	2500	flows, graphs	7m 46s	✗

Practice › Codeforces Solutions › Educational Codeforces Round 67 (Rated for Div. 2) ›

CF 1187G - Gang Up

We are given a small undirected graph representing a town, with a designated meeting point at node 1. Several people start at specified nodes and all want to reach node 1. Time is discrete, and each person can either wait at their current node or traverse one edge per minute.

Practice › Codeforces Solutions › Educational Codeforces Round 67 (Rated for Div. 2) ›

CF 1187E - Tree Painting

We are given a tree where every vertex starts unpainted, and we gradually paint vertices black. The first move can start anywhere, and after that every move must pick a white vertex that is adjacent to at least one black vertex.

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CF 1187D - Subarray Sorting

We are given two arrays of equal length and allowed to repeatedly pick any contiguous segment of the first array and sort only that segment in non-decreasing order.

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CF 1187F - Expected Square Beauty

We are given an array whose elements are not fixed numbers but independent random integers. Each position $i$ can take any integer in the interval $[li, ri]$, all values equally likely and independent across indices.

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CF 1187C - Vasya And Array

We are asked to construct any integer array of length $n$ that is consistent with a set of constraints about subarrays. Each constraint describes either that a segment must be non-decreasing or that it must fail to be non-decreasing.

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CF 1187A - Stickers and Toys

Each query describes a collection of identical eggs. Every egg contains some combination of two possible items: a sticker and a toy. Across all eggs, there are exactly s stickers and exactly t toys in total, and every egg contributes either one or both of these items.

Practice › Codeforces Solutions › Educational Codeforces Round 67 (Rated for Div. 2) ›

CF 1187B - Letters Shop

We are given a string s representing a sequence of letters available in a shop, arranged from left to right. Each customer (friend) wants to buy letters to form their name, but they can only purchase a prefix of the shop letters.