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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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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 19d ago by Lundin‭  ·  last activity 7d ago by Sylvester‭

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: ...

22 answers  ·  posted 3y ago by General Sebast1an‭  ·  last activity 11d ago by Europe2048‭

77%
+5 −0
Find the IP address class

Task Given an IP address as a string, find its IP address class. For reference, here is a table: Class Leadingbits Numberof networks Addressesper network Total addressesin class Start...

7 answers  ·  posted 3y ago by Razetime‭  ·  last activity 13d ago by Shaggy‭

71%
+3 −0
Expand a polynomial

Challenge Given the roots of a polynomial (that is, the $x$ values where the polynomial evaluates to zero), as an array of real numbers, return the polynomial's coefficients. That is, given real ...

4 answers  ·  posted 3y ago by Moshi‭  ·  last activity 14d ago by Moshi‭

60%
+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 21d ago by Shaggy‭

83%
+8 −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...

7 answers  ·  posted 8mo ago by trichoplax‭  ·  edited 26d ago by trichoplax‭

50%
+0 −0
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 1mo ago by trichoplax‭  ·  last activity 29d ago by celtschk‭

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 (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

60%
+1 −0
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

85%
+10 −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. ...

21 answers  ·  posted 2y ago by celtschk‭  ·  last activity 3mo ago by xrs‭

66%
+2 −0
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

50%
+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

71%
+3 −0
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 4mo ago by Andrew Ray‭  ·  edited 4mo ago by trichoplax‭

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

75%
+4 −0
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

50%
+0 −0
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

77%
+5 −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 2y ago by trichoplax‭  ·  last activity 5mo ago by trichoplax‭

92%
+24 −0
"Hello, World!"

Introduction The classic "Hello, World" challenge. What more can I say? Rules Program takes no input. Program outputs Hello, World! with an optional trailing newline. No other output is accep...

61 answers  ·  posted 4y ago by anna328p‭  ·  last activity 5mo ago by Lundin‭

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...

7 answers  ·  posted 3y ago by Shaggy‭  ·  last activity 5mo ago by xrs‭

84%
+9 −0
1, 2, Fizz, 4, Buzz!

The task Output the first 100 elements of the infamous FizzBuzz sequence. How? The FizzBuzz sequence is the sequence of decimal integers from 1 to 100 inclusive, but: If the integer is divisi...

21 answers  ·  posted 4y ago by Dion‭  ·  last activity 5mo ago by xrs‭

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...

33 answers  ·  posted 4y ago by moony‭  ·  last activity 6mo ago by xrs‭

71%
+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

66%
+2 −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...

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

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

71%
+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

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 11mo ago by WheatWizard‭  ·  last activity 8mo 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 8mo ago by WheatWizard‭  ·  last activity 8mo 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 9mo ago by H_H‭  ·  last activity 8mo 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 10mo ago by trichoplax‭  ·  last activity 10mo 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 1y ago by trichoplax‭  ·  last activity 11mo 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 1y ago by trichoplax‭  ·  last activity 11mo 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 1y ago by WheatWizard‭  ·  last activity 12mo 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 1y ago by H_H‭  ·  last activity 12mo ago by Arpad Horvath‭

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 1y ago by Razetime‭

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 1y ago by WheatWizard‭  ·  edited 1y ago by WheatWizard‭

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

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

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

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 3y ago by Lundin‭  ·  last activity 1y 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 2y ago by trichoplax‭  ·  edited 1y 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 1y ago by mjkatre18‭  ·  closed 1y 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 1y ago by RubenVerg‭

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

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 2y ago by trichoplax‭  ·  last activity 1y 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 1y ago by trichoplax‭  ·  last activity 1y 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 1y ago by WheatWizard‭  ·  edited 1y 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 1y ago by trichoplax‭  ·  last activity 1y 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 1y ago by trichoplax‭  ·  last activity 1y 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 3y ago by Moshi‭  ·  last activity 1y ago by RubenVerg‭