Questions tagged [code-golf]

Code-golf is a competition to solve a particular problem in the fewest bytes of source code.

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16 votes
40 answers

Implement the `<=>` three-way comparison operator on numbers

In C++, there exists a a <=> b three-way comparison operator that, for numerical types, does the following: If a < b, ...
83 votes
184 answers

Output the sign

Given a number N, output the sign of N: If N is positive, output 1 If N is negative, output -1 If N is 0, output 0 N will be an integer within the representable range of integers in your chosen ...
5 votes
2 answers

Shortening this Code to process nested tuple even further without the use of max()

I have the code: ...
47 votes
91 answers

Division and remainder

This challenge, while probably trivial in most "standard" languages, is addressed to those languages which are so esoteric, low-level, and/or difficult to use that are very rarely seen on this site. ...
12 votes
29 answers

All non-ordered pairs between the elements of an array

Task: Return an array with all possible pairs between the elements of an array. Example From a=["a", "b", "c", "d"]; return ...
58 votes
47 answers

How many steps does it take from n to 1 by subtracting the greatest divisor?

Inspired by this question over at Mathematics. The Problem Let n be a natural number ≥ 2. Take the biggest divisor of ...
11 votes
9 answers

Great Leap to the Right

Given a string s consisting of characters a-z lowercase, generate 5 arrays a1, a2, ...
2 votes
4 answers

A randomly colored walk

Given two inputs, a distance \$d\$ and a number \$n\$ output a list of \$n\$ random colors which each have distance \$d\$ from the previous. Background A random walk is a path which is defined by ...
142 votes
558 answers

Shortest infinite loop producing no output

Your task is to create the shortest infinite loop! The point of this challenge is to create an infinite loop producing no output, unlike its possible duplicate. The reason to this is because the code ...
32 votes
29 answers

Converge to a number

Your challenge is to, given a positive integer n, count up to each digit of it, giving the effect of converging on it. Basically, count up to the first digit of n by its place value (\$⌊\log_{10}\left(...
29 votes
44 answers

Visible Dice Faces

A traditional Western die is a cube, on which the integers 1 to 6 are marked on the faces. Pairs that add to 7 are placed on opposite faces. As it is cube, we can only see between 1 and 3 faces (...
16 votes
7 answers

We're gonna need a bigger podium!

If \$R\$ runners were to run a race, in how many orders could they finish such that exactly \$T\$ runners tie? Challenge Given a positive integer \$R\$ and a non-negative integer \$0\leq T\leq {R}\$ ...
170 votes
471 answers

Implement a Truth-Machine

A truth-machine (credits goes to this guy for coming up with it) is a very simple program designed to demonstrate the I/O and control flow of a language. Here's what a truth-machine does: Gets a ...
48 votes
40 answers

At least h with at least h

Input A list of nonnegative integers. Output The largest nonnegative integer h such that at least h of the numbers in the ...
81 votes
81 answers

Print some JSON

This challenge is straightforward, but hopefully, there are plenty of avenues you can approach it: You need to print/return a valid JSON object of at least 15 characters, not counting unessential ...
13 votes
51 answers

Output a string's cumulative slope

Challenge Given a string such as Hello World!, break it down into its character values: ...
148 votes
321 answers

Fibonacci function or sequence

The Fibonacci sequence is a sequence of numbers, where every number in the sequence is the sum of the two numbers preceding it. The first two numbers in the sequence are both 1. Here are the first ...
26 votes
66 answers

Minimum excluded number

This is intended to be an easy, bite-size code-golf. The mex (minimal excluded number) of a finite collection of numbers is the smallest non-negative integer ...
67 votes
134 answers

Reverse stdin and place on stdout

Requirements: Take an input on stdin including new lines / carriage returns of unlimited length (only bounded by system memory; that is, there is no inherent limit in the program.) Output the reverse ...
25 votes
24 answers

Hunt for discount

Story My local pizza delivery introduced new discount. You get 50% discount from every second item on your order. But being greedy capitalists, they forgot to mention that they will rearrange items ...
29 votes
54 answers

Create a checkerboard matrix

Take a positive integer n as input, and output a n-by-n checkerboard matrix consisting of 1 and 0. The top left digit should always be 1. Test cases: ...
15 votes
40 answers

Index and return 3 characters

The challenge is simple: Read 3 letters from a system input¹ and convert them to numbers (A-1, B-2, C-3...Z-26)². Print each of those numbers in the order the ...
15 votes
16 answers

How long to carry sort?

Carry sort is an \$O(n)\$ "sorting" algorithm. Here's how it works. The algorithm moves left to right along a list. As it traverses a list it "carries" a single item, the largest ...
26 votes
32 answers

Compute minimax of an array

Consider an array x such as [1 5 3 4] and a number n, for example ...
118 votes
397 answers

Print a 10 by 10 grid of asterisks

Background This is a standard textbook example to demonstrate for loops. This is one of the first programs I learnt when I started learning programming ~10 years ago. Task You are to print this exact ...
-6 votes
1 answer

Do absolutely nothing [closed]

Write a program that has at least one byte that, when run, does absolutely nothing. I thought this would be done by now, but I can't find any other challenges like this. How to tell if it does nothing:...
27 votes
54 answers

Alphabet to Number and Number to Alphabet

Challenge In this challenge you have to take a number as input and output the corresponding letter of the alphabet, and vice versa. (1 <=> A, 2 <=> B) etc. ...
20 votes
10 answers

How far is the Sun?

Introduction tl;dr Continuously output the current distance from the Earth to the Sun. Simplified, the orbit of the Earth around the Sun is an ellipse. So the actual distance between both is ...
55 votes
192 answers

Scream very loudly

Write a script that outputs A to stdout infinitely. There should be no newlines or separators between the characters. Standard loopholes apply. This is code-golf. ...
38 votes
14 answers

The sum is always 15

Write a program or function that takes an array of non-negative integers as input and outputs a set of vectors/arrays with the elements of the input array in order, split so that each vector sums up ...
23 votes
34 answers

Produce a m*n table in HTML

Input : Two decimal integers m and n that respectively give the number of rows and columns of the table. ...
26 votes
52 answers

Is it a pure word?

Introduction A pure word (or perfect word), as defined by me, is a word where the sum of the position in the alphabet of each letter in the word is perfectly divisible by the total length of the word. ...
52 votes
132 answers

The vanilla factorial challenge

Task Given a non-negative integer \$n\$, evaluate the factorial \$n!\$. The factorial is defined as follows: $$ n!=\begin{cases}1 & n=0\\n\times(n-1)!&n>0\end{cases} $$ Rules All default I/...
23 votes
9 answers

Blinking Lighthouses

Lighthouses on an island have blink codes that let ships know which lighthouse they are seeing. Input should be strings of S and L. Here is a (Python) example of codes for 4 lighthouses as a list of ...
8 votes
51 answers

Summing the Digits of a Number

Challenge Given a non-negative integer, find the sum of its digits. Rules Your program must take a non-negative integer as input. Your program should output the sum of the digits of the input ...
45 votes
88 answers

Determine if all decimal digits are unique

Deleted questions on Stack Overflow sometimes make for great golf material. Write a function that takes a nonnegative integer as input, and returns true if all the digits in the base 10 ...
231 votes
344 answers

Is this number a prime?

Believe it or not, we do not yet have a code golf challenge for a simple primality test. While it may not be the most interesting challenge, particularly for "usual" languages, it can be nontrivial in ...
83 votes
203 answers

Sum of all integers from 1 to n

I'm honestly surprised that this hasn't been done already. If you can find an existing thread, by all means mark this as a duplicate or let me know. Input Your input is in the form of any positive ...
108 votes
319 answers

Simple cat program

One of the most common standard tasks (especially when showcasing esoteric programming languages) is to implement a "cat program": read all of STDIN and print it to STDOUT. While this is named after ...
63 votes
153 answers

Print 0 to 100 without 1-9 characters

Print 0 to 100 without using characters 1,2,3,4,5,6,7,8,9 in your code. Seperator of numbers can be comma, whitespace or newline. Shortest code wins.
18 votes
10 answers

Recognize a counting tree

Let a counting tree be a rooted tree in which every node is labeled with the number descendants it has. We can represent such trees as ragged lists with each node being represented by a list ...
19 votes
28 answers

Alternating sums of multidimensional arrays

Given a multidimensional array, find the recursive alternating sum. An alternating sum is simply the sum of an array, where every other item (starting with the second) is negated. For example, the ...
26 votes
47 answers

Shortest Code to Find the Smallest Missing Positive Integer

Description Given an unsorted array of integers, find the smallest positive integer that does not appear in the array. Your task is to write the shortest code possible to solve this problem. Input A ...
12 votes
16 answers

Longest Valid Parentheses

Given a string of parentheses ( and ), find the length of the longest substring that forms a valid pair of parentheses. Valid ...
17 votes
24 answers

Shortest code to generate all Pythagorean triples up to a given limit

Generate the shortest possible code in any programming language that can generate all Pythagorean triples with all values not exceeding a given integer limit. A Pythagorean triple is a set of three ...
110 votes
83 answers

Draw the national flag of Iceland

This year's UEFA Euro 2016 is over and besides a couple of negative headlines there has been a very positive surprise as well – the Iceland national football team. Let's draw their national flag. ...
9 votes
31 answers

Counting Letters in a String

Write a program or function that takes in a string and outputs a count of each modern English alphabet letter in the string, case-insensitive. Input: A string consisting of printable ASCII characters (...
88 votes
116 answers

N(e(s(t))) a string

To "function nest" a string, you must: Treat the first character as a function, and the following characters as the arguments to that function. For example, if the input string was ...
8 votes
14 answers

Time to shortest permutation

Yesterday, as part of a IQ-style test, I got this interesting question: The time on a 24-hour clock is 11:43. What is the least number of minutes I should wait before the same digits are on the ...
18 votes
18 answers

"Sort" by element duplication

Inspired by one of many bugs I ran into while implementing selection sort in trilangle. Given a non-empty list of non-negative integers, "sort" the list using the following procedure: Find ...

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