Educational Codeforces Round 68 (Rated for Div. 2)

Solutions for Educational Codeforces Round 68 (Rated for Div. 2) (contest 1194). 4/7 problems verified against sample I/O. Difficulty range: 800-2700.

7 items

Educational Codeforces Round 68 (Rated for Div. 2)

Type: Div. 2 | Problems: 7 | Verified: 4/7 | Rating range: 800-2700 | Time: 29m 26s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Remove a Progression	800	math	4m 23s	✗
B	Yet Another Crosses Problem	1300	implementation	3m 1s	✓
C	From S To T	1300	implementation, strings	1m 41s	✓
D	1-2-K Game	1700	games, math	6m 6s	✗
E	Count The Rectangles	2200	bitmasks, brute-force, data-structures	4m 34s	✓
F	Crossword Expert	2400	combinatorics, dp, number-theory	2m 31s	✓
G	Another Meme Problem	2700	dp	7m 10s	✗

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CF 1194G - Another Meme Problem

We are asked to count ordered pairs of positive integers $(x, y)$ with both coordinates at most a very large bound $n$, where $n$ can have up to 100 decimal digits.

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CF 1194E - Count The Rectangles

We are given a collection of axis-aligned line segments in the plane. Each segment is either perfectly horizontal or perfectly vertical. Horizontal segments never overlap with other horizontal segments, and the same is true for vertical segments.

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CF 1194D - 1-2-K Game

We are given a single chip placed at the right end of a linear strip of cells indexed from 0 up to n. Two players alternate moves starting from the rightmost position n, and each move consists of shifting the chip left by exactly 1, 2, or k positions, as long as the chip stays…

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CF 1194A - Remove a Progression

We start with a list containing the integers from 1 to n in increasing order. The process repeatedly removes elements from this list in a very specific way: on the first step we remove the first remaining element, on the second step we remove what is now the second remaining…

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CF 1194B - Yet Another Crosses Problem

We are given several independent grids. Each grid is a matrix of characters where each cell is either already black or still white. We are allowed to turn white cells into black one at a time. The goal is to make the grid contain at least one “cross”.

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CF 1194F - Crossword Expert

We are asked to calculate the expected number of crosswords Adilbek can fully solve in a fixed amount of time, given that each crossword takes either ti or ti + 1 seconds independently with equal probability.

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CF 1194C - From S To T

We are given three strings s, t, and p. We can repeatedly take any character from p and insert it anywhere in s. The goal is to determine if, after some sequence of such insertions, s can become exactly equal to t.