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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
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

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

66%
+2 −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 4mo ago by trichoplax‭  ·  last activity 1mo ago by Shaggy‭

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+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

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+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

86%
+11 −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] -&gt; [1,2,1,2,3,3,4,5,1,2]...

18 answers  ·  posted 2y ago by rak1507‭  ·  last activity 2mo ago by dino‭

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+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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+3 −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...

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

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

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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

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+0 −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 ...

0 answers  ·  posted 3mo ago by trichoplax‭

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+0 −0
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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+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

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

81%
+7 −0
Word Set Square

Challenge Given a string, e.g. Hello, do the following: Mirror it: Hello -&gt; HelloolleH and create a right triangle using it as the sides: H ee l l l l o...

11 answers  ·  posted 2y ago by Razetime‭  ·  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

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

66%
+2 −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 4mo ago by trichoplax‭  ·  last activity 4mo 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

92%
+23 −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...

58 answers  ·  posted 2y ago by anna328p‭  ·  last activity 4mo ago by __blackjack__‭

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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

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

81%
+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

60%
+1 −0
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

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+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

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

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

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

66%
+6 −2
Multiply complex numbers.

Multiply complex numbers. 2 space-seperated ones will be input, as follows: (update: you can replace i with j or some other symbol if needed) a+bi -a+bi a-bi -a-bi where a and b are integers ...

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

87%
+12 −0
Partial Sums of Harmonic Series

Given an positive integer $n$, return the least positive integer $k$ such that the $k$th partial sum of the harmonic series is greater than or equal to $n$. For example, if $n = 2$, then $k = 4$, b...

11 answers  ·  posted 2y ago by Quintec‭  ·  last activity 5mo ago by south‭

81%
+7 −0
Reduce over the range [1..n]

Task I often need to find the factorial of a number or the sum of all numbers up to a number when cheating on math tests. To help me with this, your task is to write $F$, a generalized version of ...

14 answers  ·  posted 1y ago by user‭  ·  last activity 6mo ago by gifti‭

81%
+7 −0
Evens or Odds - you know this one

Get ready for a comparatively dry question - this is intended to be one of the "the"s of the code-golfing dictionary. Create a program which inputs a base 10 non-negative whole number (without lea...

16 answers  ·  posted 1y ago by AndrewTheCodegolfer‭  ·  last activity 6mo ago by Olin Lathrop‭

75%
+4 −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...

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

83%
+8 −0
Golf a FRACTRAN interpreter

Description From the Esolangs wiki, In Fractran, a program consists of a finite list of positive, rational numbers. The input to a program is a positive integer n. The list is then searched ...

8 answers  ·  posted 2y ago by Razetime‭  ·  last activity 8mo ago by torres‭

77%
+5 −0
A number adder, not a death adder

Create a program P1 which takes as input a base 10 number N1 (the numbers for the variables are important). Given N1, P1 will print a program P2. P2 will take as input a base 10 number N2 and outpu...

14 answers  ·  posted 1y ago by AndrewTheCodegolfer‭  ·  last activity 8mo ago by torres‭

80%
+6 −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...

9 answers  ·  posted 1y ago by Moshi‭  ·  last activity 8mo ago by south‭

60%
+4 −2
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: ...

18 answers  ·  posted 1y ago by General Sebast1an‭  ·  last activity 8mo ago by south‭

85%
+10 −0
Are All Elements Equal?

Challenge Given a list of integers &gt;= 0 , check if all of them are equal. Tests [1,1,1,1,1] -&gt; true [0,1,1,6,7] -&gt; false [1] -&gt; true [] -&gt; undefined(you do n...

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

83%
+8 −0
Solve Goldbach's Conjecture

Goldbach's Conjecture states that every even whole number greater than 2 is the sum of 2 prime numbers. Your task is to return those 2 prime numbers, given an even whole number as input. There are ...

10 answers  ·  posted 2y ago by Quintec‭  ·  last activity 8mo ago by torres‭

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+4 −0
The Pell Numbers

Introduction The Pell(no, not Bell) Numbers are a simple, Fibonacci-like sequence, defined by the following relation: $P_n=\begin{cases}0&amp;\mbox{if }n=0;\\1&amp;\mbox{if }n=1;\\2P_{n-1}+P_{n-2...

9 answers  ·  posted 2y ago by Razetime‭  ·  last activity 8mo ago by torres‭

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

81%
+7 −0
Word Count Tool

In Google Docs, the word count tool looks like this: Pages would not make sense, but your goal is to implement every other count. Definitions Words are strings of text separated by any amount ...

9 answers  ·  posted 1y ago by Quintec‭  ·  last activity 8mo ago by torres‭

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+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

80%
+6 −0
Write a Deadfish Interpreter

A rewrite of this SE question with a simpler input format and guidelines. Challenge Deadfish uses a single accumulator, on which all commands are to be performed. It has the following commands: ...

8 answers  ·  posted 2y ago by Razetime‭  ·  last activity 9mo ago by Zakk‭

85%
+10 −0
It's Hip to be Square

Challenge A catalogue type challenge that simply asks: Given an integer n (where n&gt;=0) as input return a truthy value if n is a perfect square or a falsey value if not. Rules You may take...

20 answers  ·  posted 1y ago by Shaggy‭  ·  last activity 9mo ago by Zakk‭

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...

27 answers  ·  posted 2y ago by moony‭  ·  last activity 10mo ago by celtschk‭

33%
+1 −4
Small integer swapping

In this simple challenge, create a short program that takes 2 ints as input, output them, swap their places, then output them again. Those 2 integers can't be the same number. The program with the ...

7 answers  ·  posted 1y ago by General Sebast1an‭  ·  last activity 11mo ago by south‭

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

80%
+6 −0
Shape of an array

Given a non-ragged array (an array where all sub-arrays at a particular level have the same length) of non-negative integers, answer its shape, that is, the length along every dimension. You may as...

6 answers  ·  posted 2y ago by Adám‭  ·  last activity 12mo ago by south‭

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