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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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71%
+3 −0
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...

3 answers  ·  posted 1mo ago by trichoplax‭  ·  last activity 1d ago by Arpad Horvath‭

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 21d ago by WheatWizard‭  ·  last activity 6d ago by Arpad Horvath‭

60%
+1 −0
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...

0 answers  ·  posted 12d ago by trichoplax‭

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 8mo ago by trichoplax‭  ·  edited 1mo ago by trichoplax‭

66%
+2 −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 2mo ago by honnza‭

57%
+2 −1
Fibonacci without consecutive digits

Output the Nth number in the list of Fibonacci numbers that have no consecutive digits. Input A non-negative integer. Output The Nth number in the list of Fibonacci numbers whose base 10 ...

2 answers  ·  posted 2mo ago by trichoplax‭  ·  last activity 2mo ago by ok12d‭

61%
+6 −3
Make $2 + 2 = 5$

In this challenge, add 2 integers, but if both the integers are 2, output 5. Shortest code in each language wins! Example ungolfed program in Python 3.x def add(x, y): if x == 2 and y == 2: ...

20 answers  ·  posted 2y ago by General Sebast1an‭  ·  last activity 2mo ago by isaacg‭

75%
+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 4mo ago by WheatWizard‭  ·  last activity 2mo ago by isaacg‭

66%
+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 2mo ago by WheatWizard‭  ·  last activity 2mo ago by isaacg‭

62%
+3 −1
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 3mo ago by H_H‭  ·  last activity 2mo ago by isaacg‭

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 3mo ago by trichoplax‭  ·  last activity 3mo ago by Razetime‭

66%
+2 −0
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 7mo ago by trichoplax‭  ·  last activity 5mo ago by NikNakk‭

60%
+1 −0
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 6mo ago by trichoplax‭  ·  last activity 5mo ago by NikNakk‭

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 6mo ago by WheatWizard‭  ·  last activity 5mo ago by justhalf‭

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 7mo ago by H_H‭  ·  last activity 5mo ago by Arpad Horvath‭

66%
+2 −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...

5 answers  ·  posted 6mo ago by trichoplax‭  ·  last activity 6mo ago by H_H‭

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 6mo ago by WheatWizard‭  ·  last activity 6mo ago by Razetime‭

80%
+6 −0
Digit Sum Integer Sequence (working title)

Inspired by this challenge. If anyone has any suggestions for a song title I could use for the challenge title then please leave a comment. Definition We define f(x) for a given integer as the su...

6 answers  ·  posted 2y ago by Shaggy‭  ·  last activity 7mo ago by RubenVerg‭

60%
+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 7mo ago by WheatWizard‭  ·  edited 7mo ago by WheatWizard‭

75%
+4 −0
55 fruit salad: choose your own Kolmogorov complexity

This is a fixed output challenge. It is similar to a standard Kolmogorov complexity challenge, except you get to choose your own fixed output. Given no input, output 55 fruits. You may choose any 5...

5 answers  ·  posted 1y ago by trichoplax‭  ·  last activity 7mo ago by trichoplax‭

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 8mo ago by H_H‭  ·  last activity 8mo ago by lovebuny‭

84%
+9 −0
Looping counter

Looping counter Create an infinite loop that outputs lines of asterisks, with each line containing one more asterisk. Instead of the asterisk, any printable, non-whitespace character can be used. ...

19 answers  ·  posted 2y ago by celtschk‭  ·  last activity 8mo ago by H_H‭

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 1y ago by trichoplax‭  ·  last activity 8mo ago by Karl Knechtel‭

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 8mo ago by WheatWizard‭  ·  edited 8mo ago by WheatWizard‭

80%
+6 −0
Keyword golfing

Many programming languages have the concept of keywords, special syntax items that are not just identifiers reserved by some library, but words reserved by the language itself. The challenge is to...

6 answers  ·  posted 2y ago by Lundin‭  ·  last activity 9mo ago by H_H‭

71%
+3 −0
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 1y ago by trichoplax‭  ·  edited 9mo ago by trichoplax‭

22%
+0 −5
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 9mo ago by mjkatre18‭  ·  closed 9mo ago by Mithical‭

86%
+11 −0
Can you give me half?

Challenge idea taken from: Eliseo D'Annunzio Task Provide code that evaluates to 0.5 numerically, i.e. the output must be recognized by your chosen language as a numeric value (Number, float, dou...

23 answers  ·  posted 2y ago by Razetime‭  ·  last activity 9mo ago by RubenVerg‭

86%
+11 −0
Reverse an ASCII string

Your goal is to reverse an ascii string. Given a (optionally newline or null terminated) input, output your input in reverse order, optionally followed by a newline. Terminate afterward. Function...

32 answers  ·  posted 3y ago by moony‭  ·  last activity 9mo ago by qwr‭

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 9mo ago by WheatWizard‭

71%
+3 −0
Sort letters by height

Given a sequence of lower case letters, sort them into order of height. Heights The heights of letters are dependent on font, so for this challenge the height order to be used is as defined below...

5 answers  ·  posted 1y ago by trichoplax‭  ·  last activity 9mo ago by Taeir‭

71%
+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 10mo ago by trichoplax‭  ·  last activity 9mo ago by RubenVerg‭

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 10mo ago by WheatWizard‭  ·  edited 10mo ago by WheatWizard‭

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 10mo ago by trichoplax‭  ·  last activity 10mo ago by RubenVerg‭

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 10mo ago by trichoplax‭  ·  last activity 10mo ago by RubenVerg‭

81%
+7 −0
Roll n fair dice

Challenge This is a simple randomness challenge: Given a non-negative integer $n$, and positive integer $m$, simulate rolling and summing the results of $n$ fair dice, each of which have $m$ sides...

10 answers  ·  posted 2y ago by Moshi‭  ·  last activity 10mo 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 10mo ago by WheatWizard‭

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 10mo ago by WheatWizard‭  ·  last activity 10mo ago by TheCodidacter, or rather ACodidacter‭

87%
+12 −0
Cumulative Counts

Challenge Given an array of numbers return the cumulative count of each item. This is the number of times an item has occurred so far. Examples [1,1,2,2,2,1,1,1,3,3] -> [1,2,1,2,3,3,4,5,1,2]...

19 answers  ·  posted 3y ago by rak1507‭  ·  last activity 10mo ago by WheatWizard‭

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 10mo ago by WheatWizard‭  ·  last activity 10mo 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 10mo ago by WheatWizard‭  ·  edited 10mo 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 10mo ago by WheatWizard‭  ·  last activity 10mo ago by Shaggy‭

66%
+2 −0
Connect the corners without 4 in a row

Connect opposite corners of a rectangle of characters without putting 4 characters in a row. Input Two numbers, W and H, representing the width and height of the rectangle Each number will be ...

1 answer  ·  posted 1y ago by trichoplax‭  ·  last activity 10mo ago by WheatWizard‭

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 11mo ago by WheatWizard‭  ·  edited 10mo ago by WheatWizard‭

66%
+2 −0
Count polyomino bisections

An polyomino is a non-empty connected subset of the square tiling consisting of squares joined along their edges. We will not require that polyominos be simply connected, that is they can have hole...

0 answers  ·  posted 10mo ago by WheatWizard‭

83%
+8 −0
Compute the determinant

Challenge A simple challenge: Given a two-dimensional matrix (an array of arrays) of real numbers, compute the determinant. The determinant of a matrix is a mathematical construct used in many ap...

9 answers  ·  posted 2y ago by Moshi‭  ·  last activity 1y ago by aspen138‭

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%
+3 −0
8 coexisting queens

This is a fixed output challenge. Output a textual representation of a chessboard hosting 8 queens, none of which are attacking each other. There are 92 ways of arranging them, 12 if rotations and...

5 answers  ·  posted 1y ago by trichoplax‭  ·  last activity 1y ago by m90‭

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 1y ago by trichoplax‭  ·  last activity 1y ago by A username‭

75%
+4 −0
Encode with ROT13.5

Given a string, convert all of its letters using ROT13, and all of its digits using ROT5. This is sometimes referred to as ROT13.5. Input A sequence of printable ASCII characters (character cod...

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