Educational Codeforces Round 147 (Rated for Div. 2)

Solutions for Educational Codeforces Round 147 (Rated for Div. 2) (contest 1821). 1/6 problems verified against sample I/O. Difficulty range: 800-2600.

6 items

Educational Codeforces Round 147 (Rated for Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 1/6 | Rating range: 800-2600 | Time: 12m 42s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Matching	800	combinatorics, math	1m 12s	✓
B	Sort the Subarray	1100	brute-force, greedy	1m 28s	✗
C	Tear It Apart	1300	brute-force, implementation, math	3m 12s	✗
D	Black Cells	1900	binary-search, brute-force, greedy	3m 1s	✗
E	Rearrange Brackets	2100	brute-force, dp, greedy	1m 48s	✗
F	Timber	2600	combinatorics, dp, fft	2m 1s	✗

Practice › Codeforces Solutions › Educational Codeforces Round 147 (Rated for Div. 2) ›

CF 1821F - Timber

We are asked to count the number of ways to place $m$ identical-height trees on $n$ consecutive spots in front of a shopping mall so that each tree can be felled either left or right without hitting the mall, the road, or other fallen trees.

Practice › Codeforces Solutions › Educational Codeforces Round 147 (Rated for Div. 2) ›

CF 1821D - Black Cells

We have a huge one-dimensional grid of cells, indexed from 0 to $10^{18}-1$. Each cell starts white, and we control a pointer initially at cell 0. The pointer can move one step to the right at a time.

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CF 1821E - Rearrange Brackets

We are given a sequence of parentheses that is already regular, meaning it can be fully matched into pairs without any leftover. The sequence could be something like ()(), ((())), or more complex nestings.

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CF 1821C - Tear It Apart

Thanks for providing the new failing sample. This is a different problem from the earlier input parsing bug. The code now runs, but produces wrong output, so it is a logic error in the algorithm itself. Let's analyze carefully.

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CF 1821B - Sort the Subarray

We are given two arrays of integers, the original array a and a modified array a'. The modification consists of selecting a contiguous subarray of a and sorting it in non-descending order to produce a'.

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CF 1821A - Matching

We are given a string consisting of digits and question marks. Each question mark represents an unknown digit, and we want to count all positive integers that can be formed by replacing the question marks with digits such that the resulting number has no leading zeros.