Hello 2025

9 problems from Hello 2025 (contest 2057), difficulty 800-3500. 1/9 solutions verified against sample I/O.

9 items

Hello 2025

Special | 9 problems | 1/9 verified | Difficulty 800-3500 | 17m 45s

#	Problem	Rating	Tags	Accepted	Time	✓
A	MEX Table	800	constructive-algorithms, math	27,506	1m 50s
B	Gorilla and the Exam	1000	greedy, sortings	23,272	1m 29s	✓
C	Trip to the Olympiad	1500	bitmasks, constructive-algorithms, greedy	13,794	1m 45s
D	Gifts Order	2000	data-structures, greedy, implementation	5,413	1m 54s
E1	Another Exercise on Graphs (Easy Version)	2300	binary-search, brute-force, dp	2,636	1m 44s
E2	Another Exercise on Graphs (hard version)	2500	binary-search, dfs-and-similar, dp	1,927	3m 55s
F	Formation	3300	binary-search, data-structures, dp	246	1m 37s
G	Secret Message	3000	constructive-algorithms, dfs-and-similar, math	726	1m 41s
H	Coffee Break	3500	data-structures, greedy, math	185	1m 50s

Practice › Codeforces Solutions › Hello 2025 ›

CF 2057H - Coffee Break

We are given a sequence of coffee machines aligned along a corridor. Each machine initially has a certain number of students around it, and we can manipulate student positions using a simple operation: turning off the lights in a room.

Practice › Codeforces Solutions › Hello 2025 ›

CF 2057E2 - Another Exercise on Graphs (hard version)

We are given an undirected weighted graph and a large number of queries. Each query picks two vertices and an integer k, and asks us to consider all possible paths between those vertices.

Practice › Codeforces Solutions › Hello 2025 ›

CF 2057G - Secret Message

The problem gives a rectangular grid where some cells are already blocked and cannot be used. The free cells, marked with "", form a figure on the grid.

Practice › Codeforces Solutions › Hello 2025 ›

CF 2057F - Formation

We are asked to maximize the height of pupils in a line under two rules. First, the line is initially comfortable: for every pupil, the height of the next pupil is at most double the height of the current pupil.

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CF 2057E1 - Another Exercise on Graphs (Easy Version)

We are given a connected undirected graph with up to 400 vertices and up to 400 edges. Every edge has a positive weight. For each query, we are given two vertices a and b, and a number k.

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CF 2057D - Gifts Order

We are given an array of integers representing sweater sizes. From any contiguous segment of this array, we define a score that depends on how spread out the values are and how long the segment is.

Practice › Codeforces Solutions › Hello 2025 ›

CF 2057A - MEX Table

We are asked to fill a table with n rows and m columns using each integer from 0 to nm - 1 exactly once. After filling, we compute the MEX (minimum excluded non-negative integer) for each row and each column and sum all these values. The task is to maximize this sum.

Practice › Codeforces Solutions › Hello 2025 ›

CF 2057C - Trip to the Olympiad

We are asked to pick three distinct students from a consecutive range of independence levels, such that a team metric is maximized. The team metric is the sum of all pairwise XORs of the three chosen levels.

Practice › Codeforces Solutions › Hello 2025 ›

CF 2057B - Gorilla and the Exam

We are asked to help a gorilla efficiently clear an array using a particular deletion operation. The operation works on any contiguous subarray: you choose the minimum value in that subarray, then remove every occurrence of that minimum from the chosen segment.