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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.

Filters (None)
55%
+3 −2
"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 2y ago by General Sebast1an‭  ·  last activity 1y ago by south‭

81%
+7 −0
Word Set Square

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

11 answers  ·  posted 3y ago by Razetime‭  ·  last activity 1y 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 1y ago by trichoplax‭  ·  last activity 1y ago by Razetime‭

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 3y ago by anna328p‭  ·  last activity 1y ago by __blackjack__‭

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 1y ago by Razetime‭  ·  last activity 1y ago by Moshi‭

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 1y ago by trichoplax‭  ·  edited 1y 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 2y ago by celtschk‭  ·  last activity 1y 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 1y ago by trichoplax‭  ·  edited 1y 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 1y ago by trichoplax‭  ·  last activity 1y 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 1y ago by Razetime‭  ·  last activity 1y 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 2y ago by Razetime‭  ·  last activity 1y 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 -> 8+1=9 -> 81%9=0. Your task is to find the first n Niven numbers, given n. Te...

7 answers  ·  posted 1y ago by Razetime‭  ·  last activity 1y 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 2y ago by heav‭  ·  last activity 1y 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 3y ago by Quintec‭  ·  last activity 1y 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 2y ago by user‭  ·  last activity 1y 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 2y ago by AndrewTheCodegolfer‭  ·  last activity 1y 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 2y ago by Razetime‭  ·  last activity 1y 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 3y ago by Razetime‭  ·  last activity 1y 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 2y ago by AndrewTheCodegolfer‭  ·  last activity 1y ago by torres‭

85%
+10 −0
Are All Elements Equal?

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

16 answers  ·  posted 2y ago by Razetime‭  ·  last activity 1y 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 3y ago by Quintec‭  ·  last activity 1y ago by torres‭

75%
+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&\mbox{if }n=0;\\1&\mbox{if }n=1;\\2P_{n-1}+P_{n-2...

9 answers  ·  posted 3y ago by Razetime‭  ·  last activity 1y 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 1y ago by Moshi‭  ·  last activity 1y 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 2y ago by Quintec‭  ·  last activity 1y ago by torres‭

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 2y ago by General Sebast1an‭  ·  last activity 1y 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 3y ago by Razetime‭  ·  last activity 2y 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>=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 2y ago by Shaggy‭  ·  last activity 2y ago by Zakk‭

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 2y ago by General Sebast1an‭  ·  last activity 2y 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 2y ago by General Sebast1an‭  ·  last activity 2y 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 3y ago by Adám‭  ·  last activity 2y ago by south‭

60%
+1 −0
Stairs? Stairs! Stairs.

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

7 answers  ·  posted 2y ago by General Sebast1an‭  ·  last activity 2y ago by radarek‭

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 2y ago by General Sebast1an‭  ·  last activity 2y ago by radarek‭

77%
+5 −0
Diagonalized alphabet

Task Print the following: ABDFHJLNPRTVXZ CABDFHJLNPRTVX ECABDFHJLNPRTV GECABDFHJLNPRT IGECABDFHJLNPR KIGECABDFHJLNP MKIGECABDFHJLN OMKIGECABDFHJL QOMKIGECABDFHJ SQOMKIGECABDFH USQOMKIGE...

7 answers  ·  posted 2y ago by Razetime‭  ·  last activity 2y ago by radarek‭

87%
+12 −0
Evaluate a single variable polynomial equation

Challenge Given a list of n numbers and x, compute $a + bx^1 + cx^{2} + ... + zx^{n-1}$, where a is the first value in the list, b is the second, etc. n is at most 256 and at least 0. The input va...

20 answers  ·  posted 3y ago by moony‭  ·  last activity 2y ago by south‭

77%
+5 −0
Given the preorder and the inorder of a tree, output the postorder

Definitions A binary tree is either a null (leaf), or an object (node). A node contains a value (non-negative integer) and two pointers (left and right) to two separate binary trees. A binary tre...

2 answers  ·  posted 3y ago by Hakerh400‭  ·  last activity 2y ago by radarek‭

77%
+5 −0
Prime Difference

Given an integer n, output the smallest prime such that the difference between it and the next prime is at least n. For example, if n=5, you would output 23, since the next prime is 29, and 29-23&...

8 answers  ·  posted 3y ago by Quintec‭  ·  last activity 2y ago by radarek‭

86%
+11 −0
Weave Strings Together

Given a list of strings(and optionally, their length) as input, weave the strings together. Intro Your goal is to mimic the WV operator in Pip. Take a list of strings and alternate between their ...

13 answers  ·  posted 3y ago by Razetime‭  ·  last activity 2y ago by radarek‭

86%
+11 −0
Merge two strings

Challenge Given two strings a and b, return the shortest string s so that s starts with a and ends with b. (Inspired by https://chat.stackexchange.com/transcript/message/57816868#57816868 ) Exam...

8 answers  ·  posted 3y ago by rak1507‭  ·  last activity 2y ago by radarek‭

84%
+9 −0
Coat of Many Colours

Challenge Given a list of unique colour names as input, sort them in the order that they first appear in Joseph's Amazing Technicolour Dreamcoat. Example Input: green, blue, red, brown Outpu...

6 answers  ·  posted 2y ago by Shaggy‭  ·  last activity 2y ago by radarek‭

77%
+5 −0
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 -> "abc" "Hello", 0 -> "" "double", 2 -> "ddo...

14 answers  ·  posted 2y ago by celtschk‭  ·  last activity 2y ago by south‭

81%
+7 −0
Make my number a set

Natural to set (set meaning an unordered collection with no duplicates, though answers may use and output lists instead) Recently I was brainstorming what a language with only (arbitrarily nested...

10 answers  ·  posted 3y ago by Wezl‭  ·  last activity 2y ago by radarek‭

81%
+7 −0
Bytes to Segfault

Challenge Cause the currently running program to receive the SIGSEGV signal (on Linux or other *nix systems) as fast as possible. What it does with the signal doesn't matter as long as it receives...

10 answers  ·  posted 3y ago by moony‭  ·  last activity 2y ago by radarek‭

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 2y ago by Moshi‭  ·  last activity 2y ago by radarek‭

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 2y ago by Lundin‭  ·  last activity 2y ago by radarek‭

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...

20 answers  ·  posted 3y ago by Dion‭  ·  last activity 2y ago by celtschk‭

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 2y ago by celtschk‭  ·  last activity 2y 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 2y ago by AndrewTheCodegolfer‭  ·  edited 2y ago by AndrewTheCodegolfer‭

77%
+5 −0
99 Shortened Bottles of Beer

Disclaimer This challenge also exists in CGCC, but if you want to compete here (too), then hop in! Challenge Recreate "99 Bottles of Beer on the Wall", using the least bytes possible. Lyrics: ...

13 answers  ·  posted 2y ago by General Sebast1an‭  ·  last activity 2y ago by General Sebast1an‭

75%
+4 −0
Caesar shift cipher

Introduction What is the Caesar shift cipher (ROT$n$)? It's basically a cipher sequence that changes a letter's value from the number chosen. If we use ROT1 on "games", we get "hbnft". The basic i...

7 answers  ·  posted 2y ago by General Sebast1an‭  ·  edited 2y ago by General Sebast1an‭

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 2y ago by celtschk‭  ·  last activity 2y ago by Moshi‭