Codeforces Round 906 (Div. 2)

Solutions for Codeforces Round 906 (Div. 2) (contest 1890). 2/7 problems verified against sample I/O. Difficulty range: 800-3000.

7 items

Codeforces Round 906 (Div. 2)

Type: Div. 2 | Problems: 7 | Verified: 2/7 | Rating range: 800-3000 | Time: 13m 47s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Doremy's Paint 3	800	constructive-algorithms	1m 20s	✓
B	Qingshan Loves Strings	800	constructive-algorithms, implementation	1m 52s	✗
C	Qingshan Loves Strings 2	1300	constructive-algorithms, implementation, two-pointers	1m 36s	✗
D	Doremy's Connecting Plan	1700	graphs, greedy, math	2m 18s	✓
E1	Doremy's Drying Plan (Easy Version)	2000	brute-force, data-structures, dp	2m 14s	✗
E2	Doremy's Drying Plan (Hard Version)	2600	data-structures, dp	3m 37s	✗
F	Game of Stacks	3000	dfs-and-similar, graphs, implementation	50s	✗

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CF 1890E2 - Doremy's Drying Plan (Hard Version)

We have $n$ cities arranged along a line and a forecast of rain for $m$ consecutive days. Each day's rain covers a continuous interval of cities $[li, ri]$. A city is dry if it never experiences rain across all $m$ days.

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CF 1890E1 - Doremy's Drying Plan (Easy Version)

We are given a sequence of cities numbered from 1 to $n$ and a forecast of rain for the next $m$ days. On day $i$, rain will cover the cities in the interval $[li, ri]$. A city is dry if no rain ever falls there during the $m$ days. Doremy can prevent rain on exactly two days.

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CF 1890F - Game of Stacks

Each stack belongs to a vertex. If we are currently at vertex u, we look at the top element of stack u. If the stack is empty, the process stops and returns u. Otherwise we pop the top element, jump to the vertex written on that element, and repeat.

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CF 1890B - Qingshan Loves Strings

We are given two binary strings, s and t. Qingshan wants to transform s into a string where no two consecutive characters are the same, called a "good" string. She can repeatedly insert string t anywhere in s, including at the start or end, any number of times.

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CF 1890C - Qingshan Loves Strings 2

We are given a binary string consisting only of 0s and 1s. The task is to transform it into a string that satisfies the following "good" property: for every position i in the string, the character at i must differ from the character at the symmetric position counted from the…

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CF 1890A - Doremy's Paint 3

We are given several test cases, each consisting of an array of positive integers. The task is not to construct a new array from scratch but to decide whether we can reorder the given elements so that every pair of adjacent elements in the resulting sequence has the same sum.