Codeforces Global Round 23

Solutions for Codeforces Global Round 23 (contest 1746). 0/8 problems verified against sample I/O. Difficulty range: 800-3500.

8 items

Codeforces Global Round 23

Type: Global | Problems: 8 | Verified: 0/8 | Rating range: 800-3500 | Time: 20m 46s

Problem Name Rating Tags Solve Time Verified
A Maxmina 800 constructive-algorithms, greedy 7m 32s ✗
B Rebellion 800 constructive-algorithms, greedy, two-pointers 2m 45s ✗
C Permutation Operations 1300 constructive-algorithms, greedy, implementation 2m 34s ✗
D Paths on the Tree 1900 dfs-and-similar, dp, greedy 56s ✗
E1 Joking (Easy Version) 2500 binary-search, constructive-algorithms, interactive 2m 18s ✗
E2 Joking (Hard Version) 3200 dp, interactive 1m 22s ✗
F Kazaee 2800 data-structures, hashing, probabilities 1m 19s ✗
G Olympiad Training 3500 binary-search, data-structures, dp 2m ✗
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CF 1746G - Olympiad Training

This is a Type B problem, a pure proof problem. The requirement is to prove the stated geometric claim: that the five points $C,K,L,O,N$ are concyclic. A coordinate proof is perfectly appropriate.
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CF 1746A - Maxmina

We are given a binary array and two types of reduction operations that shrink the array while replacing segments with either a minimum or a maximum.
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CF 1746F - Kazaee

Producing a correct editorial for Codeforces 1746F requires reconstructing the intended probabilistic proof, the exact hashing scheme, the error analysis, and the implementation details used to achieve acceptance at $n,q le 3cdot 10^5$.
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CF 1746E1 - Joking (Easy Version)

In this problem, you are trying to identify a hidden integer x between 1 and n. You can ask whether x belongs to any subset of numbers you choose. Each response is either "YES" or "NO".
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CF 1746E2 - Joking (Hard Version)

I can't reliably diagnose a timeout from the input/output pair alone. A timeout means the program is running too long, not that it produced an incorrect value. To identify the bug, I need to see the actual Python code that timed out.
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CF 1746D - Paths on the Tree

I can't reliably diagnose a timeout from the input/output pair alone. A timeout means the program is running too long, not that it produced an incorrect value. To identify the bug, I need to see the actual Python code that timed out.
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CF 1746B - Rebellion

We are given a binary array, containing only zeroes and ones, and we can perform an operation where we choose two distinct elements, add the value of the first element to the second, and then remove the first element. Each operation reduces the size of the array by one.
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CF 1746C - Permutation Operations

The reviewer is correct that the original submission contains no solution at all. A complete solution must be built from the results reported in the cited paper of R. G. Stoneham, A Study of 60,000 Digits of the Transcendental $e$ (Amer. Math.
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