Questions tagged [code-golf]
Code-golf is a competition to solve a particular problem in the fewest bytes of source code.
9,970
questions
8
votes
8answers
81 views
Calculate the inverse of a matrix
Somehow, we don't yet have a challenge for finding the inverse of an arbitrarily-sized square matrix, despite having ones for 3x3 and 4x4, as well as a more complex version.
Your task is, given a ...
1
vote
0answers
70 views
Is a coincident point in a pair of rotated hexagonal lattices closest to the origin?
Preface
This is a code-golf question where the technique must search or exclude from search all possibilities. As soon as I figure out how to pose it, there will be a separate code-challenge question ...
12
votes
5answers
274 views
What valence does this APL train have?
Context
In APL, trains are tacit sequences of monadic/dyadic functions that can be called with one or two arguments. We'll code something to check if a given train follows the correct structure we ...
26
votes
14answers
1k views
Is it a digit haiku?
We can read 13576870234289 digit-by-digit in English, and it makes a haiku:
one three five seven
six eight seven zero two
three four two eight nine
We say it's a &...
14
votes
8answers
1k views
The square root of the square root of the square root of the…
This code-golf challenge will give you an integer n, and ask you to count the number of positive integer sequences \$S = (a_1, a_2, \dots, a_t)\$ such that
\$a_1 + ...
7
votes
11answers
518 views
Output ISO8601 date string from seconds and nanoseconds
One reason why ISO8601 is the best date string format, is that you can simply append as much precision as you like. Given 2 integers representing seconds and nanoseconds that have passed since ...
23
votes
9answers
2k views
The Knight's Dialer
Imagine you place a knight chess piece on a phone dial pad. This chess piece moves from keys to keys in an uppercase "L" shape: two steps horizontally followed by one vertically, or one step ...
-7
votes
0answers
61 views
Chess: Is there a check? [duplicate]
You get a string representation of a chessboard. It consists of 64 characters going row wise from top left to bottom right.
The figures are denoted with: K king Q queen R rook, castle B bishop N ...
8
votes
2answers
144 views
Unscramble the letters by letter frequency analysis [closed]
You know those riddles where every letter is swapped for another letter?
E.g. you get a text like
...
15
votes
11answers
1k views
Rectangles in rectangles
This code-golf challenge will give you two positive integers n and k as inputs and have you count the number of rectangles with ...
19
votes
16answers
2k views
A Portuguese sequence of integers
Context
Consider the following sequence of integers:
$$2, 10, 12, 16, 17, 18, 19, ...$$
Can you guess the next term? Well, it is \$200\$. What about the next? It is \$201\$... In case it hasn't become ...
17
votes
5answers
460 views
Triangles with rational side lengths
This challenge will have give you a positive integer \$n\$ and ask you to output \$t(n)\$, the number of triangles (up to congruence) satisfying the three conditions:
The triangles have perimeter of ...
20
votes
18answers
1k views
Eating Persistence
Intro
Find the result of number cannibalism.
Why was 6 scared of 7? Becase 7 8 9.
Your program will have to find the result of applying the ...
1
vote
1answer
79 views
Simple “hyena” program [duplicate]
Write a program that takes a string as an input. For the input:
If the input doesn't match the source code, the program shall output the input intact. (Hence a cat)
Otherwise, the program shall fall ...
13
votes
19answers
2k views
Create an Accurate How-To Article
Here is an easy-intermediate challenge for anyone interested!
What is that?
A thing me and brother do a bit too often is this:
One of us has a problem and asks the other to explain how to do certain ...
21
votes
19answers
913 views
Sequences of distinct positive integers
The goal of this challenge is to take a positive integer n and output (in lexicographic order) all sequences \$S = [a_1, a_2, ..., a_t]\$ of distinct positive ...
6
votes
21answers
1k views
Output all of printable ASCII using all of printable ASCII
Output all 95 bytes from 0x20 to 0x7E inclusive (printable ASCII including space), in any order, each at least once. The source ...
21
votes
13answers
2k views
Decide a C integer literal
Objective
Given an ASCII string, decide whether it is a valid C integer literal.
C integer literal
A C integer literal consists of:
One of:
0 followed by zero or ...
29
votes
20answers
3k views
Looks prime to me!
Figuring out whether a given number is prime, while not very complicated, is kind of hard. But making a guess doesn't need to be.
Seeing whether a number is a multiple of 2 or 5 is easy - you can just ...
30
votes
31answers
2k views
Targeted duplicate removal
The task
In this challenge, you are given a number and a list.
Your task is to remove from the list all occurrences of the given number except the first (leftmost) one, and output the resulting list.
...
20
votes
42answers
3k views
Converting Strings to Decimals (Gone Wrong)
What?
Many programming languages, both practical and esoteric, have functions, methods, etc to convert a given string to a decimal number. This is how the process might work:
For each character in ...
11
votes
6answers
318 views
Geohash my positions
About geohash
Geohash is one of many encoding systems for geographic positions. Geohash positions have some advantages. It provides a short code instead of the two usual numbers for latitude and ...
18
votes
13answers
963 views
Find all integer pairs that produce a given Loeschian number
Inspired by and drawns from Is this number Loeschian?
A positive integer \$k\$ is a Loeschian number if
\$k\$ can be expressed as \$i^2 + j^2 + i\times j\$ for \$i\$, \$j\$ integers.
For example, ...
8
votes
2answers
205 views
Inverse quine: print everything except your program
Write a program which will eventually, given enough time, print all possible permutations of ASCII characters (both printable and non-printable) less than or equal to its length, except itself. The ...
7
votes
3answers
284 views
Shortest pristine truth machine
In this challenge, the goal is to create a pristine truth machine in as few bytes as possible. For reference, a truth machine does the following:
Takes input, which is always 0 or 1
If the input is 0,...
37
votes
17answers
2k views
Three other numbers
Given three distinct numbers from \$1\$ to \$7\$, output three other distinct numbers from \$1\$ to \$7\$, that is having no numbers in common with the original numbers. Your code must produce a ...
21
votes
12answers
2k views
Find a divisibility pattern
Background
Sometimes when I'm golfing a program, I'm presented with the following situation: I have an integer value \$x\$ on some fixed interval \$[a, b]\$, and I'd like to test whether it's in some ...
13
votes
6answers
1k views
Solve 4x4 Mastermind in exactly 5 steps
Background
Mastermind is a game of code-breaking for two players. One of the players is codemaker (Alice) and the other is codebreaker (Bob).
4x4 means that the player should guess the length-4 ...
10
votes
5answers
538 views
Parse a Scala expression
Scala isn't a very commonly used language around here. Most of those who know it like it[citation needed], but some go :\ when they encounter its user-defined ...
19
votes
16answers
2k views
Size up a number
Intro
Given a whole number \$< 100,\$ extend/shorten the english representation of the number to have as many characters as it's value.
Sandbox
Rules
Take the number \$n\$, and get it in words ...
7
votes
8answers
563 views
Count Euler's Tours
Leonhard Euler wants to visit a few friends who live in houses 2, 3, ..., N (he lives in house 1). However, because of how his city is laid out, none of the paths between any houses form a loop (so, ...
6
votes
6answers
781 views
TTT: Turing Text Tape
Introduction
Ah, INTERCAL...
As much as I'd like encourage everyone to Try it Online, text output is just painful.
According to the docs it uses the "Turing Text Model".
While an... ...
14
votes
15answers
2k views
Palindrome distance
Find what is the distance for a given string to its closest palindrome of the same length.
For this task I decided to give the characters further away from the string's center more weight (think of it ...
2
votes
4answers
415 views
Parse a nested parentheses
Objective
Mimic Haskell's reads :: ReadS ().
Or in other words, parse nested parentheses. Since the target type is () (the type ...
11
votes
1answer
374 views
Amount Of Potential Keys That'll Fit The Lock
Introduction:
You're a key maker, and want to access something from a safe that has a lock. Unfortunately, the key to that lock is lost, so you'll have to make a new one. You have access to a bunch of ...
19
votes
36answers
4k views
Is that number a Two Bit Number™️?
Let's start by defining a Two Bit Number™️:
It is a positive integer
When expressed as a binary string it has exactly 2 true bits OR
When expressed as a decimal number, it has exactly 2 of the ...
18
votes
5answers
2k views
How happy is this emoticon? (2.0)
OG post
Task
In this challenge, you will be given an string emoticon, and your task will be to output its happiness.
How?
An emoticon will always have eyes and mouth. It can also include eyebrows and ...
16
votes
27answers
2k views
Compactify the query string
Introduction
Just on Hacker news, John Resig contemplates
transforming a query “foo=1&foo=2&foo=3&blah=a&blah=b” into one that looks like this: “foo=1,2,3&blah=a,b", https://...
6
votes
2answers
299 views
Deserialize a binary tree breadth-first
Deserializing binary trees depth-first is pretty easy, but doing it breadth-first is (hopefully) harder. Your mission, should you choose to accept it, is to do the latter.
The input will be a 1-D list ...
28
votes
22answers
3k views
Circumference of an ellipse
Challenge
Unlike the circumference of a circle (which is as simple as \$2\pi r\$), the circumference of an ellipse is hard.
Given the semi-major axis \$a\$ and semi-minor axis \$b\$ of an ellipse (see ...
13
votes
8answers
1k views
What logic gates work given the input?
Introduction
Logic gates! Everyone knows them, everyone loves them (unless you're starting to learn them). Take two booleans, compare them, get a single boolean in return. ...
25
votes
19answers
3k views
Cat a mouse: ASCII art pointers
The Xerox Alto, originally released in 1973, was the first computer to feature the now-familiar angled mouse pointer. The Alto's bitmapped pointer looked like this (redrawn from Fig. 2 here):
Your ...
14
votes
15answers
642 views
Conway's Game of Points!
Rest in peace, John Horton Conway
There are a ton of different Game of Life interpreters out there! A ton!
Currently for you, getting an interpreter is just a dozen types and a couple of clicks away.
...
15
votes
10answers
1k views
Output the International Phonetic Alphabet
The International Phonetic Alphabet is a system of phonetic notation intended to be able to accurately represent every sound used in spoken language.
Unless I'm missing any, which I don't think I am, ...
2
votes
0answers
97 views
Grow in a slow-growing sequence [duplicate]
Background
There is an interesting question on MathSE about some conjectures that are disproven by extremely large counter-examples. This delightful answer tells the story of a sequence of numbers ...
31
votes
9answers
2k views
Dice Paths on a Grid
You place a standard die at the origin of a 2D grid that stretches infinitely in every direction. You place the die such that the 1 is facing upwards, the 2 is facing in the negative y direction, and ...
15
votes
16answers
1k views
Concatenations of powers and their squares
At time of writing, my reputation is \$16,256\$. As I noted in chat,
Oh cool my rep is the concatenation of two powers of 2: 16,256
Or even the concatenation of a power of 2 and its square, which is ...
-6
votes
1answer
89 views
No. Of Factors Does the Number Have [duplicate]
Create a function which takes in a input integer and then returns the number of factors it has, like if you pass 25 then it will return ...
13
votes
16answers
1k views
Plot a centered circle
Intro
Given radius \$r\$, draw a circle in the center of the screen.
Sandbox.
The Challenge
Here is a simple challenge.
Plot a circle using the formula \$x^2+y^2=r^2\$, or any other formula that will ...
20
votes
23answers
1k views
Find the result of some assignment statements
In this challenge, the goal is to find the values of some variables after a number of assignments are done. An example input:
a = 5
b = 4
c = a = b
a = 2
b = a
...
