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1232 votes
6 answers

Build a working game of Tetris in Conway's Game of Life

Here is a theoretical question - one that doesn't afford an easy answer in any case, not even the trivial one. In Conway's Game of Life, there exist constructs such as the metapixel which allow the ...
Joe Z.'s user avatar
  • 34.8k
619 votes
328 answers

Produce the number 2014 without any numbers in your source code

Note to challenge writers as per meta consensus: This question was well-received when it was posted, but challenges like this, asking answerers to Do X without using Y are likely to be poorly received....
Joe Z.'s user avatar
  • 34.8k
556 votes
1 answer

Build a digital clock in Conway's Game of Life

Your task is to build a Game of Life simulation representing a digital clock, which satisfies the following properties: The clock displays the hours and minutes in decimal (e.g. ...
Joe Z.'s user avatar
  • 34.8k
552 votes
241 answers

Showcase of Languages

Notes This thread is open and unlocked only because the community decided to make an exception. Please do not use this question as evidence that you can ask similar questions here. Please do not ...
517 votes
973 answers

"Hello, World!"

So... uh... this is a bit embarrassing. But we don't have a plain "Hello, World!" challenge yet (despite having 35 variants tagged with hello-world, and counting). While this is not the most ...
Martin Ender's user avatar
460 votes
50 answers

Images with all colors

Similar to the images on, make images where each pixel is a unique color (no color is used twice and no color is missing). Give a program that generates such an image, along with a ...
Mark Jeronimus's user avatar
429 votes
23 answers

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 ...
Dave's user avatar
  • 8,439
393 votes
49 answers

Covfefify a string

In this challenge, you must take a string matching the regex ^[a-zA-Z]+$ or whatever is reasonable (you don't have to consider uppercase or lowercase letters if you ...
Destructible Lemon's user avatar
391 votes
156 answers

Write a program that makes 2 + 2 = 5 [closed]

Write a program that seemingly adds the numbers 2 and 2 and outputs 5. This is an underhanded contest. Your program cannot output any errors. Watch out for memory holes! Input is optional. ...
qwr's user avatar
  • 12k
390 votes
36 answers

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 ...
Calvin's Hobbies's user avatar
382 votes
110 answers

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 ...
Milo's user avatar
  • 3,062
377 votes
1 answer

Regex that only matches itself

There are some pretty cool challenges out there involving regex (Self-matching regex, Regex validating regex) This may well be impossible, but is there a regex that will ONLY match itself? NOTE, ...
Dylan Madisetti's user avatar
359 votes
7 answers

Upgoat or Downgoat?

Given an image of a goat, your program should best try to identify whether the goat is upside down, or not. Examples These are examples of what the input may be. Not actual inputs Input: Output: <...
Downgoat's user avatar
  • 28.9k
336 votes
42 answers

High throughput Fizz Buzz

Fizz Buzz is a common challenge given during interviews. The challenge goes something like this: Write a program that prints the numbers from 1 to n. If a number is divisible by 3, write Fizz instead....
Omer Tuchfeld's user avatar
328 votes
178 answers

Tips for golfing in Python

What general tips do you have for golfing in Python? I'm looking for ideas which can be applied to code-golf problems and which are also at least somewhat specific to Python (e.g. "remove comments" is ...
moinudin's user avatar
  • 12.6k
326 votes
55 answers

Tweetable Mathematical Art [closed]

Integer math can generate amazing patterns when laid out over a grid. Even the most basic functions can yield stunningly elaborate designs! Your challenge Write 3 Tweetable (meaning 140 characters ...
A Frayed Knot's user avatar
318 votes
24 answers

Write Moby Dick, approximately

Here is a 1.2Mb ASCII text file containing the text of Herman Melville's Moby-Dick; or, The Whale. Your task is to write a program or function (or class, etc. -- see below) which will be given this ...
N. Virgo's user avatar
  • 7,242
306 votes
7 answers

Draw with your CPU

I have come across an article where students used network traffic to draw their university on the country's IPv6 graph. [image] Your goal is simple to tell, but hard to implement. Draw the text MAIL (...
bebe's user avatar
  • 4,214
301 votes
451 answers

Add a language to a polyglot

This is an answer-chaining challenge in which each answer builds on the previous answer. I recommend sorting the thread by "oldest" in order to be sure about the order in which the posts are ...
user avatar
289 votes
73 answers

We're no strangers to code golf, you know the rules, and so do I

Write the shortest program that prints the entire lyrics of "Never Gonna Give You Up" by Rick Astley. Rules: Must output the lyrics exactly as they appear in the above pastebin*. Here's the raw dump:...
Polynomial's user avatar
  • 4,506
278 votes
33 answers

Make it look like I'm working

Often, I find myself running a script or query that will take a significant amount of time to run. I can leave that script open and enjoy some guilt-free procrastination. Now, what if I could write a ...
SomeKittens's user avatar
  • 2,633
276 votes
141 answers

I need a program where the user inputs an array of doubles and the program outputs the array sorted

Note: This question was severely edited since I first posted it here. The rules were moved to here, read them before posting any answer to understand the purpose of this. This was the first question ...
Victor Stafusa - BozoNaCadeia's user avatar
269 votes
145 answers

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 "...
Nicola Sap's user avatar
  • 2,711
258 votes
37 answers

Paint Starry Night, objectively, in 1kB of code

Note: a 1000 point bounty is still available for this challenge, which I will create and award if anyone takes the top score without using built-in compression. Below is a ...
N. Virgo's user avatar
  • 7,242
251 votes
82 answers

Code that will only execute once

Goal The goal of this challenge is to write code that will execute once and only once. This means basically that it damages the program, script, or environment in some way. If rebooting the system ...
ojblass's user avatar
  • 2,837
247 votes
56 answers

Survival Game - Create Your Wolf

The Board The Board is a two dimensional array of cells. Cells are populated by Animals. Every day, all Animals on the Board simultaneously make one move. If two or more Animals move to the same cell, ...
Rainbolt's user avatar
  • 6,376
243 votes
453 answers

Golf you a quine for great good!

Using your language of choice, golf a quine. A quine is a non-empty computer program which takes no input and produces a copy of its own source code as its only output. No cheating -- that means ...
Rafe Kettler's user avatar
  • 2,707
239 votes
115 answers

Print every character your program doesn't have

Your task is to build a program (using only printable ASCII characters and/or tabs and newlines) that prints out exactly the characters in the printable ASCII space (...
Joe Z.'s user avatar
  • 34.8k
235 votes
184 answers

Evolution of "Hello World!"

This contest is officially over, the winner is jimmy23013. Congratulations! The challenge is to make a program that prints Hello World! to stdout. The catch is that ...
Calvin's Hobbies's user avatar
234 votes
367 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 ...
Dennis's user avatar
  • 210k
233 votes
28 answers


You have been hired for your tech knowledge as a Secret Agent's sidekick to ensure that the good guy can get his job done and the world can be saved. This is your last mission before retiring with a ...
Averroes's user avatar
  • 4,087
227 votes
63 answers

No A, just CAPS LOCK

What happens when the CapsLock key on your keyboard doesn't have a notch in it? "This hPPENS." The goal of this program is to consistently emulate keyboard misses where each A press is replaced with ...
Broadwell's user avatar
  • 1,821
219 votes
89 answers

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 ...
jimmy23013's user avatar
  • 36.9k
198 votes
215 answers

The Programming Language Quiz

Congratulations to Dennis who won both the cops' and the robbers' challenge! Calvin's Hobbies has already delivered on his promise and wrote this challenge for Dennis for winning the robbers' ...
Martin Ender's user avatar
197 votes
123 answers

I'm not the language you're looking for!

Isn't it annoying when you find a piece of code and you don't know what language it was written in? This challenge attempts to somewhat solve this. Challenge You will have to write a program that ...
Blue's user avatar
  • 28.5k
194 votes
415 answers

1, 2, Fizz, 4, Buzz

Introduction In our recent effort to collect catalogues of shortest solutions for standard programming exercises, here is PPCG's first ever vanilla FizzBuzz challenge. If you wish to see other ...
Beta Decay's user avatar
  • 23.3k
194 votes
62 answers

Mathematics is fact. Programming is not

In mathematics an exclamation mark ! often means factorial and it comes after the argument. In programming an exclamation mark ! ...
Calvin's Hobbies's user avatar
192 votes
80 answers

What? No error? [closed]

Your task is simple. Write a program that should obviously produce an error on first glance either when compiled or run, but either doesn't or produces some other unrelated error. This is a popularity ...
Jwosty's user avatar
  • 3,586
192 votes
179 answers

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 ...
Arandur's user avatar
  • 1,939
182 votes
29 answers

Do you want to code a snowman?

Here is a simple ASCII art snowman: _===_ (.,.) ( : ) ( : ) Let's make him some friends. This will be the general pattern for our ASCII art snowpeople: ...
Calvin's Hobbies's user avatar
180 votes
50 answers

Trolling the troll [closed]

A troll has captured you and is forcing you to write malware (defined as a program that damages the computer that runs it). The troll can read and understand code, but is not so good at spotting bugs. ...
Erel Segal-Halevi's user avatar
175 votes
101 answers

Programming Languages Through The Years

In this challenge, users will take turns completeing three fairly simple coding tasks in programming languages that are allowed to be progressively older. The first answer must use a programming ...
Calvin's Hobbies's user avatar
173 votes
97 answers

Tips for golfing in JavaScript

What general tips do you have for golfing in JavaScript? I'm looking for ideas that can be applied to code golf problems in general that are at least somewhat specific to JavaScript (e.g. "remove ...
mellamokb's user avatar
  • 6,073
172 votes
491 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 ...
a spaghetto's user avatar
  • 11.2k
171 votes
36 answers

Write program in your favorite language in another language [closed]

The determined Real Programmer can write Fortran programs in any language. from Real Programmers Don't Use Pascal Your task is to write program in your programming language of choice, but you are ...
el.pescado - нет войне's user avatar
169 votes
8 answers

Draw an Image as a Voronoi Map

Credits to Calvin's Hobbies for nudging my challenge idea in the right direction. Consider a set of points in the plane, which we will call sites, and associate a colour with each site. Now you can ...
Martin Ender's user avatar
168 votes
166 answers

Don't google "google"

We all know that if you google the word "google" it will break the internet. Your task is to create a function that accepts one string and returns its length, in the fewest possible Unicode ...
rybo111's user avatar
  • 4,547
168 votes
6 answers

Hyperprogramming: N+N, N×N, N^N all in one

Write a program that takes in a number N from 1 to 9 inclusive. In its native form your program should output N+N. E.g. output 2 if N is ...
Calvin's Hobbies's user avatar
167 votes
71 answers

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 ...
Stewie Griffin's user avatar
165 votes
128 answers

Trick or Treat polyglot

Since Halloween is coming up I thought I might start a fun little code golf challenge! The challenge is quite simple. You have to write a program that outputs either ...
BrainStone's user avatar
  • 1,531

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