All Questions
4,645
questions
21
votes
58
answers
3k
views
Find the occurrences of a character in an input string
Challenge
Write a program that, given a string x which is 10 characters long and a character y, outputs the number of times ...
- 227
20
votes
5
answers
3k
views
Calculate π with quadratic convergence
Write a function or complete program that takes a positive number n and performs n steps of an iterative algorithm for ...
19
votes
1
answer
719
views
Advent Challenge 1: Help Santa unlock his present vault!
Next >>
Descriptive Keywords (for searching): Make Two Matrices Equivalent, Overlap, Array, Find
Challenge
Santa has had a history of elves stealing presents from his vault in the past, so this ...
- 41.3k
18
votes
10
answers
991
views
Tips for golfing in Pip
Pip is an imperative golfing language with infix operators. It also borrows some features from functional and array programming.
What general tips do you have for golfing in Pip? I'm looking for ...
- 38k
13
votes
3
answers
1k
views
Polynomial Interpolation
Write a program that performs Polynomial Interpolation using true arbitrary precision rational numbers. The input looks like this:
f(1) = 2/3
f(2) = 4/5
f(3) = 6/7
...
You may assume that there's ...
- 10.1k
11
votes
16
answers
3k
views
Give me the Gray Code list of bit width n
The Gray Code is a sequence of binary numbers of bitwidth n where successive numbers differ only in one bit (see example output).
Reference
Example input:
...
- 1,276
11
votes
25
answers
3k
views
Cartesian product of a list with itself n times
When given a a list of values and a positive integer n, your code should output the cartesian product of the list with itself n ...
- 447
430
votes
23
answers
148k
views
Build a Compiler Bomb
Introduction
You're probably familiar with zip bombs, XML bombs, etc. Put simply, they are (relatively) small files which produce enormous output when interpreted by naïve software. The challenge ...
- 8,451
390
votes
36
answers
71k
views
American Gothic in the palette of Mona Lisa: Rearrange the pixels
You are given two true color images, the Source and the Palette. They do not necessarily have the same dimensions but it is guaranteed that their areas are the same, i.e. they have the same number of ...
- 89.3k
382
votes
110
answers
89k
views
Most creative way to display 42
Douglas Adams was born on March 11, 1952, and died when he was just 49. In honor of this wonderful writer, I challenge you to display 42 in the most creative way possible.
You could print it in the ...
- 3,062
269
votes
145
answers
37k
views
Without using numbers, get the highest salary you can. But don't exaggerate!
As I'm applying for some jobs whose job advert doesn't state the salary, I imagined a particularly evil interviewer that would give the candidate the possibility to decide their own salary ...by "...
- 2,711
219
votes
89
answers
39k
views
Make your language unusable
Try to write some code in your language and make it not satisfying our criteria of being a programming language any more.
A language satisfies our criteria (simplified version for this challenge) of ...
- 36.9k
192
votes
175
answers
20k
views
What is the smallest positive base 10 integer that can be printed by a program shorter (in characters) than itself?
I think the question as above is clear, but just in case:
Write a full program (not just a function) which prints a positive base 10 integer, optionally followed by a single newline.
Qualifying ...
- 1,939
167
votes
70
answers
24k
views
How high can you count?
Challenge:
Your task is to write as many programs / functions / snippets as you can, where each one outputs / prints / returns an integer. The first program must output the integer ...
- 46.2k
148
votes
245
answers
29k
views
Unscramble the Source Code
Note: This challenge is now closed to new cop submissions. This is to ensure that no one can post submissions that only remain uncracked because there aren't enough robbers interested in the challenge ...
- 29k
120
votes
405
answers
30k
views
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 ...
- 49.6k
105
votes
65
answers
12k
views
Find an Illegal String
The challenge is to find a string of characters that cannot appear in any legal program in your programming language of choice. That includes comments, strings, or other "non-executable" parts.
...
- 12.3k
104
votes
131
answers
20k
views
Shortest code to produce non-deterministic output
You need to produce output that is non-deterministic.
In this case, this will be defined to mean that the output will not always be the same result.
Rules:
A pseudo-random number generator that ...
- 23.3k
101
votes
79
answers
17k
views
The Rock, Paper, Scissors, Lizard, Spock Tournament of Epicness
Most Recent Leaderboard @ 2014-08-02 12:00
...
- 1,131
83
votes
192
answers
10k
views
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 ...
user45941
73
votes
155
answers
13k
views
Print X without X (cop's thread)
This is the cop's thread of a cops-and-robbers challenge. You can view the robber's thread here
A pretty common beginner style question is to print some string, but there's a catch! You need to do it ...
- 96.5k
67
votes
62
answers
4k
views
Count trailing truths
Inspired by, and in memory of, my dear friend and colleague,
Dan Baronet, 1956 – 2016. R.I.P.
He found the shortest possible APL solution to this task:
Task
Given a Boolean list, count the number of ...
- 29.9k
67
votes
20
answers
7k
views
Just repeat yourself
Write a program that outputs
Do not repeat yourself!
Your program code must respect the following constraints :
its length must be an even number
each ...
- 8,503
66
votes
47
answers
5k
views
User Appreciation Challenge #1: Dennis ♦
I got the spontaneous idea of making a series of challenges of users that have helped and continue to help the PPCG community be an enjoyable place for everyone, or maybe just specifically for me. :P
...
- 41.3k
59
votes
100
answers
8k
views
Find the smallest number that doesn't divide N
This challenge is simple enough that it's basically all in the title: you're given a positive integer N and you should return the smallest positive integer which is not a divisor of N.
An example: the ...
- 196k
56
votes
16
answers
8k
views
Extreme Fibonacci
There have been a billion iterations of Fibonacci challenges on this website, so lets spice things up with a Fibonacci challenge of a billion iterations!
Your challenge is to output the first 1000 ...
- 3,599
55
votes
9
answers
11k
views
Golf a number bigger than TREE(3)
The function TREE(k) gives the length of the longest sequence of trees T1, T2, ... where each vertex is labelled with one of k colours, the tree Ti has at most i vertices, and no tree is a minor of ...
- 7,207
54
votes
49
answers
26k
views
Outputting ordinal numbers (1st, 2nd, 3rd)
I would like to generate (as a return result of a function, or simply as the output of a program) the ordinal suffix of a positive integer concatenated to the number.
Samples:
...
- 643
53
votes
11
answers
4k
views
Unfolding the Hexagony source code
Introduction
If you're not familiar with Hexagony, it's an esoteric language created by Martin Büttner. The thing is that this language accepts multiple forms for the program. The following programs ...
- 44.3k
51
votes
48
answers
4k
views
Count sums of two squares
Given a non-negative number n, output the number of ways to express n as the sum of two squares of integers ...
- 144k
49
votes
97
answers
5k
views
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. ...
- 12.4k
49
votes
50
answers
19k
views
Display random colored pixels
I've always liked screens full of randomly colored pixels. They're interesting to look at and the programs that draw them are fun to watch.
The challenge
Fill your screen, or a graphical window, ...
- 13.8k
49
votes
48
answers
10k
views
Reverse Polish notation
You must evaluate a string written in Reverse Polish notation and output the result.
The program must accept an input and return the output. For programming languages that do not have functions to ...
user11
48
votes
83
answers
4k
views
Type uniqchars!
Given a string consisting of printable ASCII chars, produce an output consisting of its unique chars in the original order. In other words, the output is the same as the input except that a char is ...
- 104k
46
votes
10
answers
2k
views
Zigzagify a String
Write a program (or function) that takes in a non-empty string of any printable ASCII characters.
Print (or return) a zigzagging chain of the characters in the string with every neighboring pair of ...
- 89.3k
46
votes
3
answers
7k
views
Radiation Hardened Quine
As you should (hopefully) know, a radiation hardened quine is a quine that you can remove any one character from and still print its original, pre-modified source. The thing is, with most of these you ...
- 843
44
votes
90
answers
7k
views
Notcalc (Calculate the wrong answer)
Goal:
Given two natural numbers (integers from 0 to infinity), output a number that is not the sum of those numbers, but is a natural number.
Example solutions (TI-Basic):
...
- 3,723
44
votes
68
answers
8k
views
I reverse the source code, you negate the input!
Blatant rip-off of a rip-off. Go upvote those!
Your task, if you wish to accept it, is to write a program/function that outputs/returns its integer input/argument. The tricky part is that if I ...
- 29.9k
43
votes
9
answers
6k
views
Text compression and decompression — "Nevermore."
With the recent discussion about the use of compression tools in code golf, I thought it would be a nice challenge to write your own text compressor and decompressor.
Challenge:
Write two programs: ...
- 20.7k
40
votes
89
answers
11k
views
Add without addition (or any of the 4 basic arithmetic operators)
Problem:
Your goal is to add two input numbers without using any of the following math operators: +,-,*,/.
Additionally, you can't use any built-in functions that ...
- 7,989
40
votes
87
answers
6k
views
Generate ;# code
Related to: Make a ;# interpreter
In the above linked challenge the task was to create an interpreter for the esoteric language ;#.
The ...
- 2,014
39
votes
62
answers
6k
views
Zeroes at the end of a factorial
Write a program or function that finds the number of zeroes at the end of n! in base 10, where n is an input number (in any ...
- 7,349
37
votes
29
answers
6k
views
Find the number in the Champernowne constant
Introduction
In base 10, the Champernowne constant is defined by concatenating representations of successive integers. In base 10: 0.1234567891011121314151617... ...
- 44.3k
36
votes
49
answers
5k
views
Generate Monday Numbers
Monday numbers, as defined by Gamow in this question over on Puzzling, are positive integers N with the following three properties:
The decimal representation of N does not contain the digit 0
The ...
- 43.3k
35
votes
38
answers
4k
views
Is it Christmas?
Challenge
Given that Christmas is:
December
Month 12
Day 25
Every year, determine today's date, and whether or not today is Christmas.
If it is Christmas, you must print ...
- 453
34
votes
9
answers
3k
views
Who's that Pokémon? [closed]
Input: an integer N between 1 and 151
Output: the Nth Pokemon.
Rules
You may use one data file.
You may not use any already made data decompression algorithms. This includes libraries and other ...
- 6,198
34
votes
40
answers
6k
views
Render "Digital Clock Style" Numbers
Write the shortest program which will take a string of numbers (of up to at least 20 length) as input, and display the output using the standard digital clock style numbers. For instance for input 81,...
- 1,199
33
votes
5
answers
2k
views
Chain reaction of bombs
Introduction:
Before the task, here is what every element does on the map:
Plain land (X): This does nothing.
Destroyed land (...
- 44.3k
32
votes
46
answers
8k
views
Mode (most common element) of a list
Write a snippet to calculate the mode (most common number) of a list of positive integers.
For example, the mode of
d = [4,3,1,0,6,1,6,4,4,0,3,1,7,7,3,4,1,1,2,8]
...
- 709
31
votes
15
answers
3k
views
List all multiplicative partitions of n
Given a positive number n, output all distinct multiplicative partitions of n in any convenient format.
A multiplicative partition of n is a set of integers, all greater than one, such that their ...
- 39k