All Questions

943
votes
6answers
193k views

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 ...
568
votes
259answers
205k views

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 ...
494
votes
225answers
108k views

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 ...
469
votes
1answer
145k views

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. ...
430
votes
47answers
144k views

Images with all colors

Similar to the images on allrgb.com, 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 ...
393
votes
736answers
116k views

“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 ...
393
votes
156answers
232k views

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. ...
386
votes
110answers
80k 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 ...
374
votes
36answers
65k 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 ...
365
votes
17answers
78k 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 ...
361
votes
36answers
51k views

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 ...
330
votes
55answers
102k views

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 ...
326
votes
1answer
105k views

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, ...
296
votes
8answers
24k views

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: <...
290
votes
7answers
28k views

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 (...
290
votes
21answers
36k views

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 ...
280
votes
141answers
440k views

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 ...
278
votes
33answers
74k views

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 ...
244
votes
60answers
68k views

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:...
238
votes
36answers
40k views

Paint Starry Night, objectively, in 1kB of code

Note: Anders Kaseorg has been awarded the accept for now, to draw attention to his great answer, but the challenge is by no means over! There is still a 400 point bounty in the offering for anyone who ...
235
votes
56answers
46k views

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,...
233
votes
244answers
79k views

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 made. ...
233
votes
136answers
70k views

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 ...
225
votes
180answers
34k views

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 ...
222
votes
75answers
73k views

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 ...
210
votes
17answers
19k views

DISARM THE B.O.M.B.!

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 ...
209
votes
98answers
37k views

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 (...
209
votes
108answers
30k 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 "...
197
votes
81answers
24k views

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 ...
191
votes
308answers
40k views

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 ...
190
votes
56answers
16k views

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 ...
189
votes
282answers
42k views

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 ...
184
votes
204answers
39k views

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' ...
184
votes
50answers
35k views

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. ...
182
votes
85answers
32k 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 ...
177
votes
138answers
16k 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 ...
174
votes
103answers
22k views

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 ...
173
votes
47answers
28k views

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 !...
171
votes
26answers
19k views

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: ...
168
votes
36answers
22k views

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 ...
167
votes
8answers
30k views

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 ...
165
votes
95answers
37k views

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 ...
161
votes
57answers
38k views

Debunking Stroustrup's debunking of the myth “C++ is for large, complicated, programs only”

Stroustrup has recently posted a series of posts debunking popular myths about C++. The fifth myth is: “C++ is for large, complicated, programs only”. To debunk it, he wrote a simple C++ program ...
159
votes
122answers
31k views

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 ...
156
votes
146answers
51k views

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 ...
155
votes
13answers
34k views

Emulate an Intel 8086 CPU

Note: A couple of answers have arrived. Consider upvoting newer answers too. Common Lisp from happy5214 C from luser droog Java from NeatMonster Javascript from crempp C from Mike C C++ from Darius ...
152
votes
57answers
21k 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 ...
152
votes
4answers
13k views

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 ...
151
votes
15answers
26k views

Is My Swipe Pattern Legal?

Most Android smartphones allow the user to use a swipe pattern to open their phone: Certain patterns are legitimate, and others are impossible. Given an input swipe pattern, return a truthy or falsy ...
150
votes
57answers
15k views

Caveman Duels (or: Me poke you with sharp stick)

Caveman mad. Other caveman take stick but stick was for me. Caveman fight! Description Caveman need sharp stick to stab other caveman. Other caveman also try to stab with sharp stick. Caveman can ...

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