April Fools Day Contest 2023

Solutions for April Fools Day Contest 2023 (contest 1812). 8/10 problems verified against sample I/O. Difficulty range: -.

10 items

April Fools Day Contest 2023

Type: April Fools | Problems: 10 | Verified: 8/10 | Rating range: - | Time: 17m 17s

Problem Name Rating Tags Solve Time Verified
A Are You a Robot? - *special, expression-parsing, strings 2m 14s ✓
B Was it Rated? - *special, brute-force, implementation 1m 25s ✓
C Digits - *special 1m 58s ✗
D Trivial Conjecture - *special, constructive-algorithms, math 1m 28s ✓
E Not a Geometry Problem - *special, constructive-algorithms, geometry 1m 4s ✓
F Factorization - *special, number-theory 2m 5s ✓
G Colour Vision - *special, implementation 1m 14s ✓
H Expected Twist - *special, interactive 1m 24s ✗
I Mountain Climber - *special 1m 38s ✓
J Unmysterious Language - *special, constructive-algorithms, strings 2m 47s ✓
Practice › Codeforces Solutions › April Fools Day Contest 2023 ›

CF 1812J - Unmysterious Language

This is a pure input-format mismatch, not a logic error. Your program starts with: But the actual input is: So the format is: - First line: t test cases - Each test case: - one integer n - one line with n integers (a permutation / array) - There is no m at all So when the code…
codeforces competitive-programming *special constructive-algorithms strings Jun 9, 2026
Practice › Codeforces Solutions › April Fools Day Contest 2023 ›

CF 1812I - Mountain Climber

We are given a set of test cases, each consisting of a string of lowercase letters. The task is to decide, for each string, whether it satisfies a hidden property.
codeforces competitive-programming *special Jun 9, 2026
Practice › Codeforces Solutions › April Fools Day Contest 2023 ›

CF 1812H - Expected Twist

We are given a hidden array of length $n$, and the only way to interact with it is to ask for the maximum value inside any contiguous segment. Each query reveals a single number: the maximum over a chosen interval.
codeforces competitive-programming *special interactive Jun 9, 2026
Practice › Codeforces Solutions › April Fools Day Contest 2023 ›

CF 1812F - Factorization

This is a pure input-format mismatch, not a logic error. Your program starts with: But the actual input is: So the format is: - First line: t test cases - Each test case: - one integer n - one line with n integers (a permutation / array) - There is no m at all So when the code…
codeforces competitive-programming *special number-theory Jun 9, 2026
Practice › Codeforces Solutions › April Fools Day Contest 2023 ›

CF 1812G - Colour Vision

We are given two rows of colored tiles, each row having the same number of columns. Each tile can be red (R), green (G), or blue (B).
codeforces competitive-programming *special implementation Jun 9, 2026
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CF 1812E - Not a Geometry Problem

We are given three integers that should be interpreted as coordinates in a three-dimensional space. The task is to compute a single real number derived from these three values, and the sample output reveals what this quantity represents: it is the Euclidean length of the…
codeforces competitive-programming *special constructive-algorithms geometry math Jun 9, 2026
Practice › Codeforces Solutions › April Fools Day Contest 2023 ›

CF 1812D - Trivial Conjecture

We are asked to construct a number $n$ such that the first $k$ terms of its Collatz-like sequence never reach 1. The sequence is defined by repeatedly applying a function $f$ to the current number: if the number is even, divide it by 2; if it is odd, multiply by 3 and add 1.
codeforces competitive-programming *special constructive-algorithms math number-theory Jun 9, 2026
Practice › Codeforces Solutions › April Fools Day Contest 2023 ›

CF 1812A - Are You a Robot?

This is a pure input-format mismatch, not a logic error. Your program starts with: But the actual input is: So the format is: - First line: t test cases - Each test case: - one integer n - one line with n integers (a permutation / array) - There is no m at all So when the code…
codeforces competitive-programming *special expression-parsing strings Jun 9, 2026
Practice › Codeforces Solutions › April Fools Day Contest 2023 ›

CF 1812C - Digits

We are given a sequence of single-digit integers, each between 1 and 9, for multiple test cases. For each test case, the task is to compute a single number that represents a sum derived from the digits.
codeforces competitive-programming *special Jun 9, 2026
Practice › Codeforces Solutions › April Fools Day Contest 2023 ›

CF 1812B - Was it Rated?

The problem gives us a single integer, n, which represents the size of a board or set in an abstract sense. The task is to determine whether some property holds for this n - specifically, whether a certain configuration is possible.
codeforces competitive-programming *special brute-force implementation Jun 9, 2026