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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.

121 posts · Subscribe
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 3mo ago by trichoplax‭  ·  last activity 2mo ago by torres‭

71%
+3 −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 3mo ago by trichoplax‭  ·  last activity 2mo ago by Razetime‭

60%
+1 −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...

4 answers  ·  posted 3mo ago by trichoplax‭  ·  last activity 3mo ago by steffan153‭

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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 ...

0 answers  ·  posted 3mo ago by trichoplax‭

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Circle of text characters

Given a radius R, output a text representation of a circle. Input A positive integer R (strictly greater than zero) You do not need to handle values of R greater than 32 Output A square ...

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

66%
+2 −0
Pinwheel ​words

Given a word that can be rotated by 180 degrees (a half turn) about at least one of its 3 axes and continue to be composed of English alphabet letters, output one of its rotated forms. The 3 rotat...

0 answers  ·  posted 3mo ago by trichoplax‭

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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 4mo ago by trichoplax‭  ·  last activity 1mo ago by Shaggy‭

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 4mo ago by trichoplax‭  ·  last activity 1mo ago by A username‭

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+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 4mo ago by trichoplax‭  ·  last activity 3mo ago by taoh‭

60%
+1 −0
Balanced quinary quasiquine

Given an integer $N$ in balanced quinary, output the first $N$ characters of your source code if $N$ is positive, or the last $-N$ characters of your source code if $N$ is negative. Terminology ...

1 answer  ·  posted 4mo ago by trichoplax‭  ·  edited 3mo ago by trichoplax‭

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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...

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

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 4mo ago by trichoplax‭  ·  last activity 4mo ago by Razetime‭

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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 4mo ago by trichoplax‭  ·  last activity 4mo ago by Shaggy‭

60%
+1 −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 4mo ago by trichoplax‭  ·  last activity 4mo ago by Shaggy‭

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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 4mo ago by trichoplax‭  ·  edited 4mo ago by trichoplax‭

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Chequer checker

A chequer board (also spelt "checker board" in some places) is an 8 by 8 grid of squares alternating between 2 colours. Check whether a provided pattern could be a region of a chequer board. The c...

1 answer  ·  posted 4mo ago by trichoplax‭  ·  edited 4mo ago by trichoplax‭

71%
+3 −0
Presumptuous base conversion

Take an input string representing a number and convert it to decimal (base 10). However, the base of the input is not specified. Assume the input is in the smallest base for which its digits are va...

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

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 5mo ago by Razetime‭  ·  last activity 4mo ago by Moshi‭

81%
+7 −0
Find n Niven Numbers

Challenge A Niven number is a positive integer which is divisible by the sum of its digits. For example, 81 -&gt; 8+1=9 -&gt; 81%9=0. Your task is to find the first n Niven numbers, given n. Te...

7 answers  ·  posted 6mo ago by Razetime‭  ·  last activity 5mo ago by Shaggy‭

71%
+3 −0
Make a frequency table (histogram)

Challenge Given an array in any suitable format, create a frequency table for it. i.e: Pair each unique element with the number of times it appears in the array. You can return the frequency tabl...

10 answers  ·  posted 7mo ago by Razetime‭  ·  last activity 5mo ago by Moshi‭

71%
+3 −0
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 8mo ago by Moshi‭  ·  last activity 8mo ago by orthoplex‭

77%
+5 −0
Create a range grid

This challenge is based on the i. verb from J. A range grid is basically a range of m × n numbers fit into a rectangular grid with m rows and n columns. A 2×3 range grid would be: 0 1 2 3 4 5 ...

8 answers  ·  posted 9mo ago by Razetime‭  ·  last activity 5mo ago by Shaggy‭

83%
+8 −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. ...

18 answers  ·  posted 9mo ago by celtschk‭  ·  last activity 4mo ago by south‭

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...

22 answers  ·  posted 12mo ago by Razetime‭  ·  last activity 3mo ago by taoh‭

75%
+4 −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 12mo ago by Lundin‭  ·  edited 28d ago by Lundin‭

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+7 −0
Determine whether an integer is square-free

An integer is called square-free if it is not a multiple of a perfect square other than 1. For example, 42 is square-free, but 44 is not because it is a multiple of the perfect square 4 = 2². Your...

13 answers  ·  posted 1y ago by celtschk‭  ·  last activity 4mo ago by Shaggy‭

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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...

6 answers  ·  posted 1y ago by Razetime‭  ·  last activity 8mo ago by torres‭

80%
+6 −0
Golf golf challenge

The task is to create a program which displays a golf score as text. It takes 2 numbers as input, separated by space or new line: The first number is the par of the specific hole. The second nu...

5 answers  ·  posted 1y ago by Lundin‭  ·  last activity 1y ago by radarek‭

75%
+4 −0
Implement Rule 110

[Rule 110] is a Turing complete cellular automaton. It is defined as follows: Take as initial value a sequence of symbols that's infinite to both sides, which consists only of two different symbol...

1 answer  ·  posted 1y ago by celtschk‭  ·  last activity 1y ago by Moshi‭

40%
+0 −1
Tiny Turing-completeness

Your challenge today is to golf a program to interpret something Turing-complete. You may use any Turing-complete system for this so long as it is not the source language of the challenge - even a...

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

81%
+7 −0
Operation "Find The Operator"

Challenge Make a program that takes input of 3 non-negative integers: a result and 2 other values that once calculated results to the 3rd value. The program must figure out how to get the 2 fir...

5 answers  ·  posted 1y ago by General Sebast1an‭  ·  last activity 1y ago by radarek‭

71%
+3 −0
Run-length encode a byte sequence

Run-length encoding is a simple compression technique which compresses sequences of repeating identical bytes. The encoding rules for this task are as follows: Any sequence of $n$ identical bytes...

2 answers  ·  posted 1y ago by celtschk‭  ·  last activity 1y ago by Moshi‭

71%
+3 −0
Find good coalitions

As you might know, there were elections in Germany, and now the parties have to form a government coalition. Let's help them with it! A good coalition has the strict majority of seats (that is, mo...

2 answers  ·  posted 1y ago by celtschk‭  ·  last activity 1y ago by Moshi‭

71%
+3 −0
Encode and decode floating point integers

Imagine you have only one byte (8 bits) to store a value, but need to store values from $0$ to $4032$. Impossible, until you are also told that an error of 1/64 of the exact value does not matter. ...

2 answers  ·  posted 1y ago by celtschk‭  ·  last activity 1y ago by General Sebast1an‭

71%
+3 −0
Convert integer to English

Given a non-negative integer up to $999\,999\,999$, write it in English. The input number can be in any form other than English (though you'll typically want to use the native integer type of your...

3 answers  ·  posted 1y ago by celtschk‭  ·  last activity 1y ago by Moshi‭

66%
+2 −0
Reverse your quine

Challenge Write a program that prints its reversed self. For example, if your code is foo() Then it'll output: )(oof Make sure that the quine is a valid one, as defined here: No cheatin...

4 answers  ·  posted 1y ago by General Sebast1an‭  ·  last activity 1y ago by celtschk‭

75%
+4 −0
The Ludic Numbers

The Ludic Numbers are a sequence that pops up when you apply the sieve of eratosthenes to the natural numbers, completely removing the numbers every iteration. Here is how they are generated: The...

3 answers  ·  posted 1y ago by Razetime‭  ·  last activity 1y ago by General Sebast1an‭

81%
+7 −0
Collatz conjecture; Count the tries to reach $1$

Background Check out this video on the Collatz conjecture, also known as A006577. If you don't know what this is, we're given an equation of $3x + 1$, and it is applied this way: If $x$ is odd...

15 answers  ·  posted 1y ago by General Sebast1an‭  ·  last activity 8mo ago by torres‭

77%
+5 −0
Decode periodic decimal fractions

Rational numbers in decimal representation can have an infinite periodic part. One common way to write this down is to repeat the periodic digits and then add three dots. Numbers without those thre...

2 answers  ·  posted 1y ago by celtschk‭  ·  edited 1y ago by General Sebast1an‭

71%
+3 −0
Abbreviate everything

Challenge Make a program that takes input of a string and abbreviate it. All letters of an abbreviation are capitalized, so keep that in mind. Whitespace, numbers and non-English characters ar...

3 answers  ·  posted 1y ago by General Sebast1an‭  ·  last activity 1y ago by Hakerh400‭

66%
+2 −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 1y ago by Moshi‭  ·  last activity 1y ago by Moshi‭

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Repeat the characters

Given a string and a non-negative integer $n$, output a new string in which each character is repeated $n$ times. Test cases: "abc", 1 -&gt; "abc" "Hello", 0 -&gt; "" "double", 2 -&gt; "ddo...

14 answers  ·  posted 1y ago by celtschk‭  ·  last activity 1y ago by south‭

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Define a mathematical expression in English

Background Inspired by this challenge that is also a mathematical English translator. Challenge Write a program that translates a mathematical expression using English with the following specifi...

1 answer  ·  posted 1y ago by General Sebast1an‭  ·  edited 1y ago by General Sebast1an‭

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+4 −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...

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

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+1 −0
Stairs? Stairs! Stairs.

Challenge Make a program that takes input of an integer that's $n &gt; 1$ and print out a staircase using a specific character for stair basing (hashes (#) for demonstration; you can use spaces,...

7 answers  ·  posted 1y ago by General Sebast1an‭  ·  last activity 1y ago by radarek‭

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+4 −0
When The Ternary Is Balance

Inspired by this Rosetta Code article. Introduction Balanced Ternary is a method of representing integers using -1, 0 and 1 in base 3. Decimal 11 = (1 * 32) + (1 * 31) + (−1 * 30) = [1,1,-1] or ...

3 answers  ·  posted 1y ago by Razetime‭  ·  last activity 1y ago by Moshi‭

62%
+3 −1
"Hello, {name}!"

Background While we do have a "Hello, World!" challenge, we still don't have one regarding input. So let's do one! Challenge Create a program that takes an input (not as a function argument) the...

16 answers  ·  posted 1y ago by General Sebast1an‭  ·  last activity 4mo ago by south‭

71%
+3 −0
Generalized Sort

Challenge We all know and love the generic sort function, right? However, it only sorts based off one criterion - what if we want more? That's where you come in. Your task is to sort an array bas...

6 answers  ·  posted 1y ago by Moshi‭  ·  last activity 1y ago by radarek‭

66%
+2 −0
Make my value binary

Challenge What do computers understand? That's right, binary. All files are turned into binary digits when you run them, but what if I suggest giving you an int then turn it into it's binary value...

14 answers  ·  posted 1y ago by General Sebast1an‭  ·  last activity 12mo ago by Olin Lathrop‭

77%
+5 −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...

8 answers  ·  posted 1y ago by Moshi‭  ·  last activity 1y ago by radarek‭

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