Codeforces Global Round 5

9 problems from Codeforces Global Round 5 (contest 1237), difficulty 1000-3500. 3/9 solutions verified against sample I/O.

9 items

Codeforces Global Round 5

Global | 9 problems | 3/9 verified | Difficulty 1000-3500 | 44m 41s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Balanced Rating Changes	1000	implementation, math	22,113	4m 41s	✓
B	Balanced Tunnel	1300	data-structures, sortings, two-pointers	22,758	3m 15s	✓
C1	Balanced Removals (Easier)	1700	constructive-algorithms, geometry, greedy	6,300	3m 18s
C2	Balanced Removals (Harder)	1900	binary-search, constructive-algorithms, divide-and-conquer	4,534	3m 53s
D	Balanced Playlist	2000	binary-search, data-structures, implementation	4,778	5m 18s
E	Balanced Binary Search Trees	2400	dp, math	1,520	5m 37s	✓
F	Balanced Domino Placements	2600	combinatorics, dp	1,092	3m 57s
G	Balanced Distribution	3500	data-structures, dp, greedy	166	5m 50s
H	Balanced Reversals	3300	constructive-algorithms	437	8m 52s

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CF 1237H - Balanced Reversals

We are given two binary strings of equal even length, and we are only allowed to modify the first string. The only operation available is somewhat unusual: we pick a prefix of even length and reverse that prefix in place.

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CF 1237G - Balanced Distribution

We are given a circular arrangement of $n$ people, each holding some number of stones. The total number of stones is divisible by $n$, so there exists a target value $T = frac{sum ai}{n}$ such that the goal is to end with every position holding exactly $T$ stones.

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CF 1237D - Balanced Playlist

We are given a circular playlist of tracks, each with a numeric “coolness” value. Starting from any chosen track, we keep listening forward in cyclic order, revisiting tracks as needed. While listening, we maintain the maximum coolness seen so far.

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CF 1237F - Balanced Domino Placements

We are given a grid where some dominoes are already placed. Each domino always occupies exactly two adjacent cells. The placement has a special restriction: no row or column is allowed to contain cells from two different dominoes.

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CF 1237A - Balanced Rating Changes

We are given a list of integers representing rating changes from a contest. The total sum of all these changes is exactly zero, meaning gains and losses perfectly balance out before any modification. The task is to transform each value independently into a “halved” version.

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CF 1237C2 - Balanced Removals (Harder)

We are given a set of points in three-dimensional space, and we must repeatedly delete them in pairs until nothing remains. The restriction is not about distance or parity, but about geometry of axis-aligned boxes. At any moment, we pick two remaining points.

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CF 1237C1 - Balanced Removals (Easier)

We are given an even number of distinct points in 3D space. The task is to repeatedly remove points in pairs until none remain.

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CF 1237E - Balanced Binary Search Trees

We are counting a very specific family of binary search trees built on the keys from 1 to n. The tree structure must satisfy the usual BST ordering, but that is not the main constraint that drives the solution. The real restriction comes from two additional rules.

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CF 1237B - Balanced Tunnel

We are given a timeline of cars entering a tunnel and a separate timeline of the same cars exiting it. Every car appears exactly once in each list, so both sequences are permutations of the same set of identifiers. Inside the tunnel, overtaking is only detectable indirectly.