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Challenges

Code challenges of all types. For questions about golfing, bowling, etc, use Q&A. For questions about this community, use Meta. To get feedback on a challenge before posting it, use Sandbox.

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Multiplicative perfection

Given a positive integer, indicate whether it is the product of its proper divisors. Integers equal to the product of their proper divisors can be found on the Online Encyclopedia of Integer Seque...

4 answers  ·  posted 27d ago by trichoplax‭  ·  last activity 25d ago by celtschk‭

60%
+1 −0
Most isolated of 3 points

Given 3 points, output one that is separated from its nearest neighbour by the largest distance. Input 3 distinct points (that is, no 2 points are in the same position). Each point is a pair o...

0 answers  ·  posted 4mo ago by trichoplax‭  ·  edited 4mo ago by trichoplax‭

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+1 −0
How many odd digits?

Given a positive integer, count its odd digits. Input An integer from 1 to 999,999,999, inclusive, in any of the following formats: A number (such as an integer or floating point number), li...

6 answers  ·  posted 2mo ago by trichoplax‭  ·  last activity 17d ago by Shaggy‭

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+0 −0
Net​​ or​​ not?

Given a hexomino, indicate whether it is a net of a cube. Input A 6 by 6 grid containing exactly 6 filled squares. The 6 filled squares will be in a single edge connected set (a hexomino). Th...

0 answers  ·  posted 3mo ago by trichoplax‭

75%
+4 −0
Source with the whole alphabet in order of appearance

The challenge is to write as short a source as possible, where the English alphabet (in alphabetical order from top to bottom) "abcdefghijklmnopqrstuvwxyz" is a sub-sequence of the source code. Th...

5 answers  ·  posted 15d ago by Lundin‭  ·  last activity 3d ago by Sylvester‭

66%
+2 −0
Construct the Irish possessive

In this challenge you will take an Irish word and a personal pronoun and create the possessive pronoun construction combining the two. For example sé, madra becomes a mhadra. Translated to English...

1 answer  ·  posted 7mo ago by WheatWizard‭  ·  last activity 7mo ago by Arpad Horvath‭

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+2 −0
Can I follow this recipe?

You work in a kitchen which has a peculiar rule. When you mix something into a pot you must always add at least one new ingredient. So you can add pasta, oil, salt then pesto, but not pasta, pesto...

1 answer  ·  posted 8mo ago by WheatWizard‭  ·  last activity 8mo ago by isaacg‭

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+3 −0
12-hour time is weird

Your mission for today, should you choose to accept it, is to write a simple 12-hour clock calculator. Your input will always be in the form of arg op arg, where op is either + or -, and arg is eit...

0 answers  ·  posted 8mo ago by honnza‭

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Borromean coprimes

Given 3 positive integers, indicate whether they are Borromean coprimes. Definition 3 positive integers are called Borromean coprimes if both of the following are true: Their greatest common d...

2 answers  ·  posted 1y ago by trichoplax‭  ·  last activity 11mo ago by NikNakk‭

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Substring factor

Does a positive integer have a substring as a factor? Input A positive integer. Output One of 2 distinct values to indicate whether the input has a factor that is a strict substring of it...

3 answers  ·  posted 4mo ago by trichoplax‭  ·  last activity 3mo ago by Shaggy‭

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Hex ​​​detector

Given an integer from 1 to 1000, indicate whether it is a centered hexagonal number[1] (also known as a hex number). What is a hex number? The hex numbers can be visualised as follows: On a he...

4 answers  ·  posted 4mo ago by trichoplax‭  ·  last activity 2mo ago by trichoplax‭

75%
+4 −0
Calculate the Z-array

Task Given a list of numbers $X$ produce a second list of numbers $Y$ such that $Y_i$ is the length of the longest common prefix of $X$ and $X$ with the first $i$ elements removed. For example if...

1 answer  ·  posted 1y ago by WheatWizard‭  ·  last activity 1y ago by TheCodidacter, or rather ACodidacter‭

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Fibonacci without consecutive digits

Output the Nth number in the list of Fibonacci numbers that have no consecutive digits. Input A non-negative integer (if you treat the Fibonacci numbers as zero-indexed) or a positive integer (...

4 answers  ·  posted 9mo ago by trichoplax‭  ·  last activity 2mo ago by Andrew Ray‭

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Shortest representation in generalised Roman numerals

Find the shortest representation of an integer in generalised Roman numerals. Since there is more than one way to generalise, only the following definition applies to this challenge. Definition T...

1 answer  ·  posted 1y ago by trichoplax‭  ·  last activity 11mo ago by NikNakk‭

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Round trip stones

$N$ vessels initially contain $3$ stones each. What is the probability of having at least $3$ stones in the first vessel after moving a uniformly random selection from the first vessel to the secon...

1 answer  ·  posted 7mo ago by trichoplax‭  ·  last activity 6mo ago by Arpad Horvath‭

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Towers of DC .:.

DC is a reverse-Polish calculator REPL that is available on most Linux distributions. In reverse-Polish notation, you can push values to a stack and then pop those values back off to perform operat...

0 answers  ·  posted 3mo ago by Andrew Ray‭  ·  edited 3mo ago by trichoplax‭

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+3 −0
Single digit Roman numeral

Given a single character, which is a valid Roman numeral, output its value. Values There are 7 valid single character Roman numerals, with the following values: Character Value I...

6 answers  ·  posted 1y ago by trichoplax‭  ·  last activity 6mo ago by xrs‭

75%
+4 −0
Probability of rolling all 6 dice faces

The probability of rolling every number from 1 to 6 with $N$ six-sided dice. Input A positive integer $N$. Your code must work for inputs up to and including 10, but may crash, error, or give ...

4 answers  ·  posted 1y ago by trichoplax‭  ·  last activity 1y ago by RubenVerg‭

83%
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The 50 substrings that validate any string of Roman numerals

Given a string of Roman numerals, decide whether it forms a valid Roman number. If not, output the substring that proves this, from the list of 50 strings described below. Relevant fact This chal...

7 answers  ·  posted 8mo ago by trichoplax‭  ·  edited 22d ago by trichoplax‭

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+4 −0
Is it stuck in a counting loop?

Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it (not necessarily contiguously). So f [1,1,2,2,1,3,3] = [1,2,1,2,3,1...

1 answer  ·  posted 11mo ago by WheatWizard‭  ·  last activity 8mo ago by isaacg‭

60%
+1 −0
Reverse engineer the colors for a layout.

At my job we have to sometimes lay out materials. Materials come in large long rolls and are cut into smaller pieces when being laid out. When we order the rolls we draw up a layout document which...

0 answers  ·  posted 1y ago by WheatWizard‭

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Fibonascii Squares

The Challenge Your job is to, given input positive non-zero integer $n$, output an ASCII representation of the tiled Fibonacci squares up to the $n$th number of the Fibonacci sequence. Rules Inp...

2 answers  ·  posted 5mo ago by Sylvester‭  ·  edited 4mo ago by Sylvester‭

71%
+3 −0
How many umbrellas to cover the beach?

You work at a beach. In the afternoon, the sun gets quite hot and beachgoers want to be shaded. So you put out umbrellas. When you put out umbrellas you want to shade the entire beach, with as few ...

2 answers  ·  posted 1y ago by WheatWizard‭  ·  last activity 12mo ago by justhalf‭

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+3 −0
Label a hinged tetromino

Given a hinged tetromino, give it a unique, consistent label independent of location, rotation, and reflection. Tetrominoes A tetromino is a connected subset of the square tiling, composed of 4 s...

2 answers  ·  posted 1y ago by trichoplax‭  ·  last activity 1y ago by RubenVerg‭

66%
+2 −0
Prove commutativity on this monoid presentation.

Given two binary strings $A$ and $B$ such that $A$ is an anagram of $B$, output a third binary string $S$ such that both $A$ and $B$ can be created by iterated removals of the substring $10101$ fro...

0 answers  ·  posted 1y ago by WheatWizard‭

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+1 −0
I irradiate your source code, you irradiate your output

Your task is to write a program $p$ which outputs a string $s$ with the same length as $p$, where $s \neq p$. If I remove the $n$th byte from your program to get program $q$, then either $q$ outpu...

0 answers  ·  posted 1y ago by WheatWizard‭  ·  edited 1y ago by WheatWizard‭

81%
+7 −0
Efficient censorship

You are a low-level censor working for the Ministry of Media Accuracy. Part of your job is to make sure that certain words don't appear in publications. Every morning you get a fresh stack of next...

4 answers  ·  posted 1y ago by WheatWizard‭  ·  last activity 1y ago by Shaggy‭

60%
+1 −0
Word suggesting

Suggest a word from a word list, given a string. Motivation Imagine typing a word one letter at a time, and seeing a suggested word after each letter is typed. At first the suggested word is simp...

1 answer  ·  posted 1y ago by trichoplax‭  ·  edited 8mo ago by trichoplax‭

66%
+2 −0
Is it a valid hidden word?

The Universal Crossword has a set of guidelines for crossword puzzle submissions. In this challenge we are going to be concerned with their rules for hidden word themes. A hidden word clue consis...

1 answer  ·  posted 1y ago by WheatWizard‭  ·  last activity 12mo ago by Razetime‭

62%
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Print the modular multiplicative inverse / virtual fractions

Goal Print the modular multiplicative inverse with a modulus of 65536 (or a higher exponent of 2) for odd numbers 1-97. Example output Print these values (or an extension of them): 1 43691 52...

1 answer  ·  posted 9mo ago by H_H‭  ·  last activity 8mo ago by isaacg‭

57%
+2 −1
Give the fool's fibonacci sequence

Recently I asked for tips on improving some code-golf of mine. The code was supposed to output every third value of the Fibonacci sequence starting with 2: 2,8,34,144,610,2584,10946,46368,196418,...

0 answers  ·  posted 1y ago by WheatWizard‭  ·  edited 1y ago by WheatWizard‭

71%
+3 −0
Plain black webpage

This is a language specific challenge, for HTML only. Your answer is the content of a self contained HTML file, that when opened in a web browser gives a plain black page. Requirements The HTM...

4 answers  ·  posted 10mo ago by trichoplax‭  ·  last activity 9mo ago by Razetime‭

66%
+2 −0
Digit antitranspose

Convert a matrix or grid of digits to its antitranspose. For a square matrix , this is its reflection in its antidiagonal. More generally, for a rectangular matrix, this is its reflection in its sk...

4 answers  ·  posted 2y ago by trichoplax‭  ·  last activity 2y ago by torres‭

66%
+2 −0
Build a replacement ball in regex.

In this challenge you will take a number $n$ and a string $X$ of length $\geq n$, and produce a regular expression which matches all strings that are withing $n$ character substitutions of $X$. Sp...

3 answers  ·  posted 1y ago by WheatWizard‭  ·  last activity 1y ago by WheatWizard‭

66%
+2 −0
Find near miss prime multiples.

Given a number $n \geq 3$ as input output the smallest number $k$ such that the modular residues of $k$ by the first $n$ primes is exactly $\{-1,0,1\}$. That is there is a prime in the first $n$ p...

0 answers  ·  posted 1y ago by WheatWizard‭  ·  edited 1y ago by WheatWizard‭

66%
+2 −0
Are these reduced forms of the same thing?

Task You are going to take three strings as input $A$, $B$ and $X$. And your goal is to determine if there exists a third string $S$ such that both $A$ and $B$ can be formed by iteratively removin...

0 answers  ·  posted 1y ago by WheatWizard‭  ·  edited 1y ago by WheatWizard‭

75%
+4 −0
Knight safe squares

Given a chess board with some knights on it, say how many squares are neither attacked by a knight nor containing a knight. Input An 8 by 8 grid where each square is either a knight or empty T...

3 answers  ·  posted 2y ago by trichoplax‭  ·  last activity 1y ago by Karl Knechtel‭

66%
+2 −0
Is it part of the mandelbrot set?

Input is a number, you have to decide if it is part of the mandelbrot set or not, after at least 16 iterations. This is done by applying this formula: $z_n = z_{n-1}^2 + c$ repeatedly. $c$ is the ...

1 answer  ·  posted 1y ago by H_H‭  ·  last activity 12mo ago by Arpad Horvath‭

66%
+2 −0
Reverse the bits in a Byte

Simple challenge: Read a byte, swap bit 7 with 0, 6 with 1, 5 with 2 and 4 with 3 and then output the byte. For example the byte 0b1001'1100 would turn into 0b0011'1001. Rules: Shortest code wi...

6 answers  ·  posted 1y ago by H_H‭  ·  last activity 1y ago by lovebuny‭

22%
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HOW TO HANDLE THIS ERROR: "Failed to get input map for signature: serving_default" [closed]

import requests import json import numpy as np import base64 import cv2 Replace this with the actual image path you want to test image_path = 'H_L_.jpg' Read and preprocess the image image ...

0 answers  ·  posted 1y ago by mjkatre18‭  ·  closed 1y ago by Mithical‭

66%
+2 −0
Mark my beacons

Given a grid of numbers, mark the concentric areas around nonzero elements (beacons) decreasing from the value of the beacon till 1. For example, here are some grids with a single beacon: Size 1:...

0 answers  ·  posted 2y ago by Razetime‭  ·  last activity 2y ago by Moshi‭

71%
+3 −0
The holeyest base

Given a positive integer as input, indicate which base from 2 to 16 gives the most holes in the representation of the input in that base. The digits used are 0123456789ABCDEF. Note that these incl...

6 answers  ·  posted 2y ago by trichoplax‭  ·  last activity 2y ago by Razetime‭

66%
+2 −0
Expected value of highest dice rolled

You roll $N$ six-sided dice simultaneously. Your score is the highest number rolled. If you play this game many times, what is the expected value (mean) of your score? Input A positive integer ...

2 answers  ·  posted 1y ago by trichoplax‭  ·  last activity 1y ago by RubenVerg‭

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Rationalise recurring binary

Given a potentially recurring binary string, output the number it represents, as a fraction in lowest terms. The notation used in this challenge for recurring digits is non-standard. An r is used ...

0 answers  ·  posted 2y ago by trichoplax‭  ·  edited 5mo ago by trichoplax‭

71%
+3 −0
Mediocre pop count

Given a sequence of letters, omit those with the highest or lowest pop count. Terminology The pop count or population count of a binary string is the number of 1s in it. For this challenge, the ...

6 answers  ·  posted 2y ago by trichoplax‭  ·  last activity 2y ago by A username‭

66%
+2 −0
Determine if a polyomino is "prime"

An $n$-polyomino is a connected subset of the square tiling consisting of $n$ squares. We will not require that polyominos be simply connected, that is they can have holes. We will say a $n$-polyo...

1 answer  ·  posted 1y ago by WheatWizard‭  ·  edited 1y ago by WheatWizard‭

75%
+4 −0
Decoding a non injective bit matrix encoding

The problem Someone has created an encoding format for square bit matrices, however they have found it isn't perfect! One encoding may not decode to exactly one matrix, or it may not even be possi...

0 answers  ·  posted 1y ago by Aftermost2167‭  ·  edited 1y ago by Aftermost2167‭

71%
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Lowercase, but not just the letters

Given a string of printable ASCII characters, convert them all to lowercase, except not just the letters. ASCII characters that are letters have a bit in their binary representation that is 0 for ...

7 answers  ·  posted 2y ago by trichoplax‭  ·  edited 1y ago by trichoplax‭

71%
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From the smallest seed

Challenge It's a bootstrapping challenge this time! Write a full program that, once run, writes the source code of another program that in turn, once run, writes the source code for another progra...

2 answers  ·  posted 2y ago by Moshi‭  ·  last activity 2y ago by orthoplex‭

75%
+4 −0
Just the vowels please

Given a sequence of letters, output only the vowels. Input A sequence of letters This may be a string or any ordered data structure of characters (provided it is consistent between inputs) Th...

9 answers  ·  posted 2y ago by trichoplax‭  ·  last activity 2y ago by taoh‭