# All Questions

10,369 questions
537 views

### Plight of the Concorde

Background The traveling salesman problem (TSP) asks for the shortest circuit that visits a given collection of cities. For the purposes of this question, the cities will be points in the plane and ...
3k views

### Find the needle in the haystack

Given a rectangular haystack of size at least 2x2 composed of all the same printable ASCII characters, output the location (counting from the top-left) of the needle which is a different character. ...
208 views

### This ain't it Chief

This is mostly for the memes. I regret existing. Rules Your code has to output, by either printing or showing in stdout, the phrase This ain't it Chief. in that ...
763 views

### Make a longer lenguage program

Lenguage is a brainfuck dialect that is notorious for breaking source restriction challenges. That is because Lenguage cares only about the length of it's source and not the contents. First, the ...
316 views

### A Multipurpose Quine

I personally love quines, but they all seem to be so... static. So why not create a quine that can do more. Challenge The challenge here is to create a quine that without any sort of input is a ...
10k views

### There's a hole in the bottom of the sea

Whilst trying (and failing) have persuade my infant son to eat his dinner, I tried singing to him. Mid way through this song I realised the formulaic structure might lend itself well to code golfing! ...
198 views

### A Radiation Hardened Palindromic Quine

There are radiation hardened quines, palindromic quines, but has anyone tried both?! I think not! Rules So the challenge here is to make a quine that if any symbol is deleted it prints its original ...
672 views

### Find a Rocco number

I was asked this question in an interview but I was unable to figure out any solution. I don't know whether the question was right or not. I tried a lot but couldn't reach any solution. Honestly ...
253 views

### Ambiguous Locations on a Grid

You have a little robot with four distance sensors. It knows the layout of a room, but it has no sense of orientation other than being able to lock onto the grid orientation. You want to be able to ...
1k views

Growing up, my first console game system was an Atari 2600 and I will always have a love for some of those games I so enjoyed as a child. Many of the graphics are still memorable, perhaps even iconic....
388 views

### Trapped Knight Sequence

Introduction Inspired by the very recent video The Trapped Knight - Numberphile, I came up with a challenge. The trapped knight sequence is a finite integer sequence of length 2016, starting from 1, ...
7k views

### Sum of Powers of 2

The Challenge Given an integer input x where 1 <= x <= 255, return the results of powers of two that when summed give <...
11 views

### How does the community work? [migrated]

How does this Programming Puzzles & Code Golf work? Just curious because I don't really know what this is and I want to fined out...
1k views

### The Path Of The Wildebeest

Golf a program or function which gives the $n^{\text{th}}$ location of the wildebeest who starts at square $1$ on an infinite chessboard which is numbered in an anti-clockwise square spiral, where ...
1k views

### Spot all (anti)diagonals with duplicated values

Challenge: Given a matrix input, determine the amount of diagonals and anti-diagonals with duplicated numbers. So if we have a matrix like this: ...
1k views

### Draw a path made by direction changers

This challenge takes place on a grid. ...
264 views

### Partition a square grid into parts of equal area

This challenge is based on the following puzzle: You are given an n by n grid with n cells ...
3k views

### Pointer jumping

Suppose we have an array $\texttt{ps}$ of length $n$ with pointers pointing to some location in the array: The process of "pointer jumping" will set every pointer to the location the pointer it ...
451 views

### Prime Difference [duplicate]

Given an integer n, output the smallest prime such that the difference between it and the next prime is at least n. For example, if n=5, you would output ...
5k views

### Who will win the election?

This is a challenge in which two people, 1 and 2, are running for office. People deterministically vote in certain ways in the world of 1 and 2, which can allow for the candidates to figure out the ...
676 views

### Binary self-rotation

Given a binary 3D array, for each layer, cyclically rotate up each of its columns as many steps as indicated by the binary encoding of the columns of the layer above it, and then cyclically rotate ...
134 views

### No-alphanumeric code exec

Introduction In most interpreted languages, there is an operation that will run code generated at runtime. It generally requires alphanumeric characters to refer to this operation. Write a program, ...
2k views

### Connect 4: Spot the Fake!

The bank has been broken into, and all the local mafia thugs have an unusual alibi: they were at home playing Connect 4! In order to assist with the investigation, you are asked to write a program to ...
272 views

### Count the Closed Polygons

Input: An NxM grid or multi-line string (or other reasonable input-format), containing only printable ASCII (unicode range ...
3k views

It is very hard to remember my password, so I came up with a way to generate a password. The way I generate my password is from a word or a sentence, following these steps: Start from left to right ...
308 views

### Matrix rotation sort

Lets define a non-empty, unsorted and finite matrix with unique numbers as follow: $$N = \begin{Bmatrix} 4&5&7\\1&3&6 \end{Bmatrix}$$ Lets define 4 matrix moves as: ↑* (up): Moves a ...
4k views

### Increment a GUID

Inspired by a recent Daily WTF article... Write a program or function that takes a GUID (string in the format XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX, where each X ...
238 views

### Is it Valid Modified UTF-8?

UTF-8 is a relatively simple way to encode Unicode codepoints in a variable-width format such that it doesn't easily confuse code that isn't Unicode aware. UTF-8 overview Bytes in the range of 1-...
6k views

### Dig a border trench

Background: Too many illegal immigrants from Blandia are crossing the border to Astan. The emperor of Astan has tasked you with digging a trench to keep them out, and Blandia must pay for the expenses....
3k views

### Equal, sum or difference!

Write shortest possible code that will return true if the two given integer values are equal or their sum or absolute difference is 5. Example test cases: ...
179 views

### Work out $x^y$ using only addition and subtraction [duplicate]

The challenge is to implement a function or program that takes two numbers, $x$ and $y$ and return the result of $x^y$. The program cannot use any other mathematical operation other than $+$ ...
78 views

### Chess move validation [duplicate]

Write a program that accepts chess moves, validate them and shows the results. The program should: Check wheter or not a move is valid Check if a king is in check or in checkmate Process the changes ...
3k views

### Matrix Jigsaw Puzzles

Input: An integer n Two equal-sized square matrices (with their width/height being a multiple of n) Output: One of two ...
1k views

### Unix timestamp to datetime string

Given a unix timestamp as an input, give a datetime string, in a format like so: "YYMMDD.HHmm" Rules The input is a number (integer) of a millisecond-precise UNIX epoch time (milliseconds since 1970 ...
317 views

### Matrix Jigsaw Puzzle Pieces

(Randomly inspired by https://codegolf.meta.stackexchange.com/a/17272/42963) Given a rectangular matrix of digits (i.e., 0 - 9), output the "pieces" of the matrix ...
639 views

### Number of $n$-carbon alkanes

Given a positive number $n$, find the number of alkanes with $n$ carbon atoms, ignoring stereoisomers; or equivalently, the number of unlabeled trees with $n$ nodes, such that every node has ...
4k views

### What are the repeating Fibonacci Digits?

As you probably know, a Fibonacci Number is one which is the sum of the previous two numbers in the series. A Fibonacci Digit™ is one which is the sum of the two previous digits. For instance, for ...
254 views

### Nested lists as printable 2D objects [closed]

I don't know if something like this exists already (and I'm not finding the right key words) but if not, it felt like it could be an interesting coding puzzle. The challenge is, to take an ...
284 views

### Range interval insert which should split into unique ranges

Given a range and a list thereof, while keeping the existing intervals in the list unchanged, split the additional range into sub-intervals and add them to the list, such that all the ranges in the ...
472 views

### An Séimhiú agus an tUrú

An Séimhiú agus an tUrú In Irish Gaelic (Gaeilge) there are a number of ways that the start of a word can be changed. The most common of these are lenition (an séimhiú) and eclipsis (an t-urú) ...
2k views

### Enumerate each series of identical numbers in-place

Given a list of strictly positive integers, go through each distinct number and replace all occurrences of it with successive indices (zero or one based) of a new series. Examples ...
407 views

### Mis-decode a date

Background Inspired by a now deleted question by John Burger from which I quote: Now obviously no human made this mistake. It's a mis-decode of something - perhaps the ISBN? My question is: ...
2k views

### Multi-level marketing “legs” investment rule

Multi-level marketing related challenge. A peer wants to get rewarded. So it attracted N investors (N>=1), each i-th ...
127 views

### Pattern Finder - Find Repeated Pattern in String [closed]

Introduction This is a little challenge with the goal of identifying repeated pattern "blocks" in a string, and outputting them with their frequency of occurence from left to right. A friend asked ...
841 views

### Write a function/method that takes in a string and spells that word out using the NATO Phonetic Alphabet. Titlecase optional

Write a program that takes in a string and spells that word out using the NATO Phonetic Alphabet. The mapping is as follows: ...
1k views

### How many consecutive descending numbers in my number?

2019 has come and probably everyone has noticed the peculiarity of this number: it's in fact composed by two sub-numbers (20 and 19) representing a sequence of consecutive descending numbers. ...
239 views

### Execute Triangularity Move

TL;DR for those not interested: Look at the test cases at the bottom. Have a program/function that outputs the 2D list displayed for the given input. Introduction: On November 15th, 2018 puzzle ...
1k views

### Clock (transliterate) Cipher

Introduction: I have loads of different ciphers stored in a document I once compiled as a kid, I picked a few of the ones I thought were best suitable for challenges (not too trivial, and not too ...