Codeforces Global Round 17

Solutions for Codeforces Global Round 17 (contest 1610). 2/9 problems verified against sample I/O. Difficulty range: 900-3300.

9 items

Codeforces Global Round 17

Type: Global | Problems: 9 | Verified: 2/9 | Rating range: 900-3300 | Time: 26m 50s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Anti Light's Cell Guessing	900	math	1m 13s	✓
B	Kalindrome Array	1100	greedy, two-pointers	1m 51s	✓
C	Keshi Is Throwing a Party	1600	binary-search, greedy	1m 48s	✗
D	Not Quite Lee	2000	combinatorics, dp, math	1m 48s	✗
E	AmShZ and G.O.A.T.	2300	binary-search, brute-force, greedy	1m 49s	✗
F	Mashtali: a Space Oddysey	3000	constructive-algorithms, dfs-and-similar, graphs	12m 34s	✗
G	AmShZ Wins a Bet	3300	data-structures, greedy, hashing	1m 54s	✗
H	Squid Game	3100	data-structures, dfs-and-similar, greedy	1m 53s	✗
I	Mashtali vs AtCoder	3100	games, trees	2m	✗

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CF 1610F - Mashtali: a Space Oddysey

We are given an undirected weighted graph where each edge has a weight of either 1 or 2. Our task is to assign a direction to each edge to maximize the number of vertices whose outgoing and incoming edge sums differ by exactly 1.

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CF 1610I - Mashtali vs AtCoder

We are given a tree of $n$ vertices. The game is played on the tree by two players who take turns deleting edges. After an edge is removed, any connected component that contains no “pinned” vertex is completely discarded. The first player who cannot make a move loses.

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CF 1610H - Squid Game

We are given a tree with n vertices and m players. Each player selects two vertices on the tree, which we will call xi and yi. A player can only be eliminated if Mashtali chooses a vertex v and the closest vertex w to v on the path from xi to yi is strictly between xi and yi.

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CF 1610G - AmShZ Wins a Bet

We are given a string of parentheses S that has been modified by repeatedly performing a wrapping operation. Each operation allows you to take any contiguous substring B and surround it with a pair of parentheses, inserting it back into its original place in the string.

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CF 1610E - AmShZ and G.O.A.T.

We are given a nondecreasing array and asked to remove as few elements as possible so that the remaining array avoids a very specific kind of “badness” condition.

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CF 1610D - Not Quite Lee

We are given an array and we look at every non-empty subsequence of it. Each subsequence is interpreted as a list of lengths, and for every length $bi$ we are allowed to build a contiguous block of exactly $bi$ consecutive integers.

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CF 1610B - Kalindrome Array

We are given an array and allowed to perform a very specific type of transformation: we may pick one value x and remove any occurrences of that value from the array, not necessarily all of them.

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CF 1610C - Keshi Is Throwing a Party

We are given a collection of people where each person has a fixed wealth equal to their index, so person 1 has 1 dollar, person 2 has 2 dollars, and so on up to n. We want to choose a subset of these people to invite to a party. Each person comes with two constraints.

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CF 1610A - Anti Light's Cell Guessing

We are given a rectangular grid with $n$ rows and $m$ columns. Somewhere inside this grid, an adversary hides a single cell $(x, y)$. We are allowed to “probe” a fixed set of $k$ cells of our choice. For each chosen cell, we receive its Manhattan distance to the hidden cell.