A code challenge is a competition for creative ways to solve a programming puzzle with an objective winning criterion not covered by other scoring tags (e.g. code-golf).

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Change the order of execution during run-time

Challenge time! Write a piece of code that takes any arbitrary code (method calls etc.) and changes the order of their execution during run-time WITHOUT using if-else. Bonus points if the number of ...
17
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8answers
1k views

Short Deadfish Numbers

Deadfish is one of the best known non Turing-complete programming languages. It has only one accumulator (which starts at 0) to store data, and only four commands: i - Increment the accumulator s - ...
15
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3answers
926 views

Hungry Image Snake - Hole #3

Hole #1 Joe the snake is hungry. He eats pictures, one pixel at a time. He really likes bright pixels. The Challenge Program Joe to eat the most bright pixels he can find, given that he can only ...
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3answers
914 views

Write a square program that outputs the number of times it has been “unrolled”

Consider a square block of text, N characters wide by N tall, for some odd integer N greater than 1. As an example let N = 5 and the text be: MLKJI NWVUH OXYTG PQRSF ABCDE Notice that this is the ...
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13answers
4k views

Programming with a Sporadic Shift Key

There's something wrong with your keyboard. The Shift key has a mind of its own. Every time you type a character you have no idea whether it will come out shifted or not (though it is 50-50). Besides ...
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2answers
364 views

Turn nouns into plurals

Your task is to take as input an English noun and output its plural. To win the challenge you must trade off code length against accuracy. Entries will be scored according to this comma-separated ...
23
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6answers
1k views

Swipe Type Converter

The next revolution in typing on laptops was released on the first of April, 2014 by SwiftKey. However, I want to be the first person to write a swiping nano clone, but, as I can't find a good ...
7
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2answers
182 views

Stabilize a Brick Structure

Bricks and Stability Defined This question uses the same definition of bricks and stability as Is the brick structure stable? Let [__] represent a masonry brick and . . ...
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8answers
2k views

Prolific Perfect Pangram Programs Pertaining to Printable ASCII

Updates: Time limit removed. You must be able to describe output - see new rule. A pangram is a sentence that uses every letter in the alphabet at least once, such as: The quick brown fox ...
15
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2answers
470 views

Construct n-gons with a ruler and compass

The task is to draw a regular polygon of n sides using only a compass and an unmarked ruler. Input (n) is one of the following 10 numbers: 3, 4, 5, 6, 8, 10, 12, 15, 16, 17. Method: Because you only ...
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7answers
1k views

The Reaction Time Game

Game The game is simple. Test the user's response time by asking them to enter the correct value that is displayed on the screen in the shortest time possible. Each round of the game will be as ...
3
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5answers
390 views

Find X in a partially sorted Array

Your job is to find the location (read index) of a given element X in an array gone through the following transformation process: Take a fully sorted integer array of size N (N is known implicitly) ...
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4answers
2k views

Enclose 1009 pixels

Output is a shape that encloses 1009 pixels. The shape must take the form of a single, closed, non-intersecting loop. Input is a positive non-zero integer. Each input must yield output that is ...
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3answers
384 views

Help me with trigonometry!

Thank you guys so much for your help with calculus. Now I need some help with my upcoming trigonometry test. On the test, I'll need to simplify expressions. I’ll be given input like 4sin(x)/(2cos(x)) ...
12
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8answers
635 views

Comment-free polyglot

Polyglots are programs that are valid in multiple programming languages simultaneously. Most such polyglots are written in such a way that certain constructs of one language are interpreted as ...
5
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4answers
608 views

Un-hash the Java Hash

Hash Un-hashing The basic goal of this challenge is to exploit the high probability of collision in the Java Hash function to create a list of plausible inputs that created an outputted hash. The ...
15
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4answers
754 views

Program a 2048 AI using an existing Framework

EDIT : Recently, my question has been proposed as a duplicate of 2048 Bot Challenge. I would like to stress that this question is different from that question, and will require answers to be ...
10
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4answers
884 views

5 Seconds to Find Pie

Pi times e (or Pie if you like ambiguous notation) to 100 decimal places is: 8.5397342226735670654635508695465744950348885357651149618796011301792286111573308075725638697104739439... (OIES A019609) ...
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1answer
405 views

Frogger Champion

The Game Most of us know about Frogger, the 80's era arcade game where the objective is to hop a frog safely across a busy highway and a hazard-filled pond to arrive safely at home. A challenge was ...
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2answers
404 views

Rolling digital number lock [duplicate]

There's a simple digital number lock. After each button press the lock checks if the previous four presses constitute the correct code. I.e. typing 44445 tests two codes: 4444 and 4445. You must brute ...
7
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7answers
2k views

The Bowlers-Golfers Fraction War

Introduction Let's start by arranging all fractions from 0 to 1 in order of lowest denominator, then lowest numerator: 1/2, 1/3, 2/3, 1/4, 3/4, 1/5, 2/5, 3/5, 4/5, 1/6, 5/6, 1/7... Note that ...
10
votes
3answers
472 views

Sort some apples!

Problem Imagine 7 buckets lined up in a row. Each bucket can contain at most 2 apples. There are 13 apples labeled 1 through 13. They are distributed among the 7 buckets. For example, {5,4}, {8,10}, ...
23
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5answers
2k views

Radioactive Quines

A radioactive quine is a quine-like program that has an even number of characters and, when run, outputs itself with exactly half of its characters removed. The output itself may be a radioactive ...
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0answers
252 views

Detect Duplicate Questions

Detect Duplicate Questions Once upon a time, there was a golfing site. It had a problem: people would post similar or identical questions again and again. You have been chosen selected forced ...
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3answers
883 views

Restricted memory optimization

The edit (or Levenshtein) distance between two strings is the minimal number of single character insertions, deletions and substitutions needed to transform one string into the other. If the two ...
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2answers
132 views

SPCL (Society for the Prevention of Cruelty to Loopholes) [closed]

I am a founder member of the above society. Maybe that's why people keep telling me I'm special. I want to raise the profile of loopholes. I am looking for a program which exhibits as many ...
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10answers
1k views

How to slow down a drunkard on his way home

Consider a square n by n grid graph that looks like this. It is important to notice that this graph is 11 by 11. At any given point a man stands at an intersection and he only ever moves ...
12
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2answers
476 views

How long is your (language) snake?

Following on from the third order quine challenge, your task is to write an Ouroboros program that uses as many languages as possible. That is, in language A, write a program pA which outputs program ...
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4answers
1k views

Can you beat the optimizer?

This is an optimization/algorithms challenge. Given two sets of points X and Y, which are to be thought of as points on a circle of circumference T, the challenge is to find the rotation which ...
33
votes
23answers
6k views

Rosetta Stone Challenge: What's Average Anyways?

The goal of a Rosetta Stone Challenge is to write solutions in as many languages as possible. Show off your programming multilingualism! The Challenge When people use the term "average," they ...
44
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17answers
6k views

mastermind horse battery staple

Objective Given a list of three-word passphrases, crack them all. Each time you guess, you will be given a clue in the style of Mastermind, depicting how many characters match the password, and how ...
5
votes
3answers
858 views

Another Euler Brick in the Wall

A Euler Brick is a cuboid where the length of all the edges are integers and all of the diagonals of the faces are integers as well. All sides must also be different. Your program has to find as ...
21
votes
1answer
1k views

Domino Circuits

Scoreboard Here are the raw scores (i.e. domino counts) for VisualMelon's submission. I'll turn these into the normalised scores described below, when more answers come in. The existing solution can ...
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1answer
601 views

Horror Movie Search Party

Plot: Jimmy is missing; we have to find him. We should split up. Plot twist: Jimmy is already dead. But, our cast doesn't know that, so they need to search the whole area anyway. There is an N ...
5
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1answer
209 views

fit 22 (perhaps 23) of a specific 3d pentacube into a 5x5 cube

The original problem is stated here over at math.SE The task is writing a program that fits 22 copies (or perhaps 23) of the following pentacube into a 5x5x5 cube (back and front view). The ...
46
votes
6answers
2k views

ASCII Art Calendar

Let's make an ASCII art clock and calendar that tells us the current month, day of the month, day of the week, hour, minute, and whether it's night or day (but not the year or second). At any ...
7
votes
5answers
963 views

Find the craftiest prime

Intro Consider the process of taking some positive integer n in some base b and replacing each digit with its representation in the base of the digit to the right. If the digit to the right is a 0, ...
30
votes
14answers
7k views

Programming Dichotomies (Literally)

Consider a question written in plain English whose answer involves two reasonably accurate (but potentially clever) words or phrases that can be separated by the word 'and': Q: What are the two ...
12
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1answer
423 views

Fusing Fireworks

Overview Given a list of fireworks a-z and times 3-78, arrange them with fuses to make them all light up at the correct time. A line of input is given as space separated letters and numbers: a 3 b ...
60
votes
15answers
5k views

Implement the Game of Life on anything but a regular grid

Conway's Game of Life is (almost) always played on a regular square grid, but it doesn't need to be. Write a program that implements the standard cell neighboring rules from Conway's Game of Life on ...
37
votes
12answers
6k views

What's the shortest contiguous subset of ASCII you need to output the rest?

The printable ASCII characters (hex codes 20 to 7E) in order are: !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~ (Note that space is in ...
7
votes
1answer
203 views

Minimal cover of bases for quadratic residue testing of squareness

Challenge Find the smallest cover of bases (e.g., moduli) whose sets of quadratic residue can be tested via table-lookup to definitively determine whether or not a given non-negative integer n is a ...
2
votes
6answers
328 views

sort and restore a set of bytes in optimal form

Challenge For any given input Y of length >= 1024 bytes: sort in ascending or descending order -- your choice generate output Q, where Q = [sorted data] + [restore information] restore Y using Q as ...
14
votes
3answers
543 views

Find the shortest bracket numbers

Bracket numbers provide a simple way to express large integers using only left bracket, space, and right bracket ([ ]). A bracket number is defined as a string of one or more pairs of matching ...
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votes
2answers
272 views

Find prime which is generating longest primes sequence using p(n+1)=(p(n)^2+1)/2

Consider following recurrence relation: p[n + 1] = (p[n]^2 + 1) / 2 If p[1], p[2], ..., p[k] are primes and p[k+1] is not, then k is length of sequence starting with p[1]. For example, if p[1] = 3, ...
28
votes
10answers
4k views

Find the largest prime whose length, sum and product is prime

The number 113 is the first prime whose length 3 is prime, digital sum 5 = 1 + 1 + 3 is prime, and digital product 3 = 1 * 1 * 3 is prime. A prime that has these 3 properties will be called supremely ...
23
votes
3answers
976 views

Where are the runs in this infinite string? (CCCCCC Found!)

Starting with the string ABC, consider the result of repeatedly appending the last half of itself to itself (using the larger half if the length is odd). We get the progression: ABC ABCBC ABCBCCBC ...
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13answers
1k views

Khinchin's constant to as many decimal places as possible in 64 bytes or less

Khinchin's constant is a curious mathematical constant that, according to Wolfram MathWold, is "notoriously difficult to calculate to high precision". Here it is to 100 digits: ...
0
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2answers
413 views

Conway's Game of Life with smallest *set* of source characters [duplicate]

The goal of this challenge is to write a program that will simulate a single round of Conway's Game of Life on an existing grid. Input format: Input will be read from stdin. The input will consist ...
14
votes
2answers
533 views

Maximum number of PEP8 violations in a single line

Your task is to write a file which contains a line with many pep8 violations. The rules: We use pep8 version 1.5.7 and the default settings. Calling pep8 with other command line options or ...