Codeforces Global Round 26

Solutions for Codeforces Global Round 26 (contest 1984). 3/9 problems verified against sample I/O. Difficulty range: 800-3300.

9 items

Codeforces Global Round 26

Type: Global | Problems: 9 | Verified: 3/9 | Rating range: 800-3300 | Time: 23m 19s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Strange Splitting	800	constructive-algorithms	2m 46s	✗
B	Large Addition	1100	implementation, math	1m 50s	✓
C1	Magnitude (Easy Version)	1300	dp, greedy, math	1m 53s	✗
C2	Magnitude (Hard Version)	1700	combinatorics, dp, greedy	2m 41s	✓
D	''a'' String Problem	2000	brute-force, hashing, implementation	2m 7s	✗
E	Shuffle	2400	dp, greedy, trees	5m 45s	✗
F	Reconstruction	2500	brute-force, dp, math	1m 59s	✗
G	Magic Trick II	3200	constructive-algorithms, implementation, sortings	2m 17s	✗
H	Tower Capturing	3300	combinatorics, dp, geometry	2m 1s	✓

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CF 1984E - Shuffle

We are given a tree with n nodes, and we can perform a single “shuffle” operation on it. The shuffle consists of picking any node as the new root, removing it from the tree, recursively shuffling each resulting subtree, and then attaching all the shuffled subtree roots back…

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CF 1984H - Tower Capturing

We are given a set of $n$ towers located at distinct points in the plane, with the guarantee that no three towers are collinear and no four towers lie on the same circle. You initially control two of these towers. The goal is to "capture" all towers by a series of operations.

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CF 1984G - Magic Trick II

We are given a permutation of numbers from 1 to n. The task is to sort this permutation using a special operation that allows moving a continuous subarray of length k to any position in the array.

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CF 1984F - Reconstruction

We are given a hidden integer array a of length n, where each element must stay within the range [-m, m]. We never see a, but instead we are given a sequence of constraints that describe either prefix sums or suffix sums of this array.

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CF 1984C2 - Magnitude (Hard Version)

We process the array from left to right while maintaining a value c, initially 0. For every element a[i], we have two choices. We may replace c with c + a[i], or replace it with Among all possible procedures, let k be the largest final value that can be achieved.

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CF 1984D - ''a'' String Problem

We are asked to find the number of nonempty strings $t neq "a"$ such that a given string $s$ can be split into pieces where each piece is either $t$ or the single character "a", with the additional constraint that at least one piece must equal $t$.

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CF 1984A - Strange Splitting

Codeforces 1984A: Strange Splitting

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CF 1984C1 - Magnitude (Easy Version)

We are processing a sequence of numbers while maintaining a running value that starts at zero. At each position, we must decide between two actions: either add the current number directly, or add it and then take the absolute value of the result.

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CF 1984B - Large Addition

We are given a number $x$, and we want to decide whether it can be expressed as the sum of two positive integers that satisfy a very specific digit restriction. Each of the two addends must have all digits in the range 5 to 9, and both numbers must have the same number of digits.