# All Questions

10,298 questions
337 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....
373 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 difference is 5. Example test cases: ...
75 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 $+$ ...
68 views

### One way road algorithm [on hold]

In a certain region all places are the one by road. But one-way traffic for all roads; if you are allowed to go from A to B via the direct route, you can not along that road from B to A. If you want ...
71 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 ...
69 views

### Givean a Tetris matrix, list all pieces [closed]

Say you have a simple tetris "game". Each piece have 1 single colour, and you read moves as: *Type *Rotation *Column of the first left piece's square inside matrix. Pieces fall till the end or ...
282 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 ...
87 views

### Custom check digit algorithm [closed]

Your challenge is to create a simple Check-Digit algorithm. Inputs: Dictionary - set of unique characters, for example "ABCDEF") Length - integer Input digit - this is what we are calculating the ...
443 views
+100

### 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 ...
105 views

### Find is string is magic or not [closed]

A string is a magic string if It consists of only digits Is a concatenation of 8 unique integers between 1 and 80 Challenge Write code which, given a string as input, outputs all the lists of ...
71 views

### Add to number using regex [closed]

Using a regular expression, I want to add 1 to 1 to get 2, 1 to 2 to get 3, 1 to 3 to get 4, 1 to 22 to get 23, 1 to 145 to get 146, etc. So I would have the expression, the value, the replacement, ...
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 ...
77 views

### Split Longer Message to multiple short messages [duplicate]

Post short messages limited to 50 Example "I can't believe Tweeter now supports chunking my messages, so I don't have to do it myself." This is 91 ...
221 views

### Nested lists as printable 2D objects [on hold]

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 ...
271 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 ...
41 views

### Matlab Question - How to optimize parameters for two data sets [closed]

This is rather an easy problem but I cannot get my head around. I have two curves in the form, say F(xi,fi) and G(xi,gi), with i = 1 to 65. F and G are supposed to be the same, but I get them ...
421 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 ...
374 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 ...
116 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 ...
482 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. ...
226 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 ...
10k views

### Oreoorererereoo

Oreoorererereoo Given an input string that is similar to the word "oreo", give an ASCII representation of the cookie that is as wide as the input string (to ensure cookie stability). Rules The ...
261 views

### Surreal Numbers

Surreal Numbers Surreal numbers are one way of describing numbers using sets. In this challenge you will determine the value of a surreal number. Intro A surreal number consists of two sets: a left ...
75 views

### Remove indentation [duplicate]

Write a program which removes any common leading spaces from the input string. For example, if the least indented line started with 3 spaces, and every other line has ...
791 views

### Length of the Longest Descent

Your task is to determine the length of the longest descent down a "mountain" represented as a grid of integer heights. A "descent" is any path from a starting cell to orthogonally adjacent cells with ...
1k views

### Find if a list is an ABC-triple

Three positive integers A, B, C are ABC-triple if they are coprime, with A < B and satisfying the relation : A + B = C Examples : 1, 8, 9 is an ABC-triple ...
139 views

### Min-Max GHC command line error bytes to bytes of source code

GHC command line errors can be horrible, lets make them as bad as possible. To disincentivize very long programs use the following formula to calculate your "score". ...
96 views

### Order of Elements of the Rubik's Cube [duplicate]

Introduction All the possible moves and their combinations of a Rubik's Cube form a group. A group in general is a set with some binary operation defined on it. It must contain a neutral element with ...
45 views

### Polynomial to String [duplicate]

I'm new to code-golf, but I was trying to solve this problem myself, and thought there must be a much "better"/shorter way of doing it. Given a sequence (list) of numbers $a_0, a_1,\cdots,a_n$, ...
2k views

### Collapsing numbers

Let's define the a function on natural numbers $n$, written as base 10 digits $d_k\; d_{k-1}\; \dotsc\; d_1\; d_0$, as follows: As long as there are equal adjacent digits $d_i\;d_{i-1}$, ...
1k views

### Get the date of the nth day of week in a given year and month

Introduction Often, people refer to dates as the "second Friday in August, 2018" or the "fourth Sunday in March, 2012". But it's hard to tell what date that is! Your task to is to write a program ...
735 views

### Most contributing rows

Given a non-empty matrix of non-negative integers, answer which unique rows contribute most to the sum total of elements in the matrix. Answer by any reasonable indication, for example a mask of the ...
421 views

### Count the contiguous submatrices

Migrated from chat Given two non-empty non-negative integer matrices A and B, answer the number of times A occurs as a contiguous, possibly overlapping, submatrix in B. Examples/Rules 0. There may ...
96 views

### All the digisibles [duplicate]

A natural number (written in the decimal base) is qualified as digisible if and only if it fulfills the following 3 conditions: none of its digits is zero, all the digits that compose it are ...
184 views

### Find equally-weighted complete graphs

Graph theory is used to study the relations between objects. A graph is composed of vertices and edges in a diagram such as this: ...
399 views

### Corrupting A Binary File By Interpreting It As Text

Using FTP's ASCII mode to transfer binary files is a bad idea. It is likely to corrupt your data. Badly. Let's simulate this corruption! Your task is to write a program which takes a file as input ...
2k views

### Eight coins for the fair king

This is a "counterpart" of another puzzle, Eight coins for the fair king on Puzzling.SE. You can read the above puzzle for the background. The details about this puzzle are as follows. A set of 8 ...
5k views

### Encode the date in Christmas Eve format

The day this post was published was Christmas Eve. Tomorrow will be Christmas. Yesterday was Christmas Eve Eve. In two days it will be ...
204 views

### Pumping quine radix

Inspired (you don't need to know them for this challenge) by the Pumping Lemma for various languages, I propose the following challenge: choose some basis $B \geq 2$ and an integer $n \geq 0$ ...
1k views

### Dungeon Crawler

Input A binary matrix $M$ representing the walls of a dungeon. The position $(x,y)$ of the player within the dungeon. The direction $d$ that the player is currently facing (0 = North, 1 = East, ...
354 views

### Just Twice Is Nice

Let's have string multiplication to take a string and a positive number and concatenate that string that many times. In Haskell: ...
1k views

### Does this Set Represent a Natural Number?

In set theory, the natural numbers $\mathbb{N} = \{0, 1, 2, 3, ...\}$ are usually encoded as pure sets, that is sets which only contain the empty set or other sets that are pure. However, not all ...