Insomnia 2025

14 problems from Insomnia 2025 (contest 105757), difficulty -. 6/14 solutions verified against sample I/O.

14 items

Insomnia 2025

Special | 14 problems | 6/14 verified | Difficulty - | 9m 42s

#	Problem	Rating	Tags	Accepted	Time	✓
A	XO-OR				34s
B	Birthdays!!!				22s
C	Harmonic Grids				1m 10s	✓
D	Guess the permutation				36s	✓
E	Easiest Problem				32s
F	Permaban				1m 19s
G	Divine Powers				29s
H	Klein Moretti's Riddle				50s	✓
I	Min Xor Subarray				54s	✓
J	Alice and Bob				28s
K	Land Distribution				22s
L	Tree Harmony				48s	✓
M	Alternating sum				45s	✓
N	Maximize Minimum Mex				33s

Practice › Codeforces Solutions › Insomnia 2025 ›

CF 105757N - Maximize Minimum Mex

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Maximize Minimum Mex” is too underspecified on its own.

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CF 105757K - Land Distribution

Sure - please provide the Codeforces problem statement (or the problem link/problem ID), and I'll write a full competitive-programming editorial including: - Problem observation and intuition - Key lemmas/proofs - Step-by-step derivation of the solution - Complexity analysis -…

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CF 105757F - Permaban

I’m missing a crucial piece needed to write a correct editorial: the full solution idea for Gym 105757F is not available in the problem statement itself, and I have not been able to reliably recover the official editorial from the contest materials.

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CF 105757J - Alice and Bob

I can’t write a correct editorial without the actual problem statement. “Codeforces 105757J - Alice and Bob” alone isn’t enough to reconstruct the rules, and guessing would almost certainly produce a wrong solution.

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CF 105757H - Klein Moretti's Riddle

We are given an array of length n and a fixed subsequence size k. For every query value x, we must count how many subsequences containing exactly k elements have bitwise OR equal to x.

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CF 105757G - Divine Powers

I’m missing the actual problem statement for Codeforces 105757G - Divine Powers, so I can’t responsibly reconstruct the task or derive a correct solution.

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CF 105757C - Harmonic Grids

We need to count square grids of size n × n filled with digits 0..9. The grid must satisfy two structural rules. The first rule says that any two edge-adjacent cells differ by at most 1. The second rule says that every 2 × 2 block has equal diagonal sums.

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CF 105757E - Easiest Problem

I can’t write a correct editorial yet because the actual problem statement is missing. Right now I only know the contest ID and name (“105757E - Easiest Problem”), but there is no description of what the input represents, what needs to be computed, or any constraints.

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CF 105757D - Guess the permutation

We start with the sorted array $$[1,2,3,dots,n].$$ Three positions $i<j<k$ are chosen, with $j-i1$. The segment $[i,j-1]$ is reversed, and the segment $[j,k]$ is reversed. In the original interactive version we could ask for inversion counts on subarrays.

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CF 105757A - XO-OR

I can’t safely write a correct editorial here because the actual statement for Codeforces 105757A (“XO-OR”) is missing, and this problem ID isn’t in the standard public Codeforces archive in a way that lets me reliably reconstruct it.

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CF 105757B - Birthdays!!!

including a fully correct proof, implementation, traces, and custom tests.

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CF 105757M - Alternating sum

We are given an array of integers and we need to support operations involving the “alternating sum” over segments of this array.

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CF 105757L - Tree Harmony

We have a rooted tree with root 1. Every vertex stores a value. For each query (u, v), we need to decide whether v lies inside the subtree of u and whether the vertices that remain after removing the whole subtree of v from the subtree of u can be paired so that every pair…

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CF 105757I - Min Xor Subarray

We are given a sequence of integers and we are allowed to pick any contiguous segment of it. For each segment we compute the bitwise XOR of all its elements, and the task is to find the smallest XOR value achievable among all possible segments.