All Questions

Background There's a common riddle that goes something like this: A snail is at the bottom of a 30 foot well. Every day the snail is able to climb up 3 feet. At night when they sleep, they slide ...

Related: Interquine Program A outputs program B's code when run, and B outputs C's source, and C outputs A's source. This time you can't exchange two characters and exchange again :) Requirements: ...

Background The background comes from this related challenge. Thanks, @HeyLlama! The "Look and say" or "Say what you see" sequence is a series of numbers where each describes the last. 1 11 (one one)...

Overview Related. When you have a very long number, you would like to say how many of a specific digits are there rather than the number itself. You may want to repeat this multiple times. Write a ...

Inputs A list (array) of numbers, or numerical strings if that makes it easier. You can assume there will always be at least two elements in the list and every element will be a natural number (...

Some days ago I found that R combn function is very slow. That function it's used to generate all combinations of the elements of x taken m at a time. I was specially interested in m = 2. Then I ...

Although related challenges have been asked, this one is different to warrant its own question. Challenge Given a positive integer, return the longest sequence of consecutive positive odd integers ...

Inputs: Two single digits (let's call them m and n) and two chars (let's call them a and b) in your input format of choice. Output: For the walkthrough, pretend m=2, n=5, a='a', b='b'. Your output ...

Given a positive integer n ≤ 500: Find the smallest positive integer k such that all digits in the decimal representation of n*k are either 0 or d, with 1 ≤ d ≤ 9. Print or return d in less than 30 ...

Whenever you make a move on a Rubik's Cube, there is a reverse move which undoes the first move. Because of this, every algorithm (set of moves) has a reverse algorithm which undoes the first ...

Ok I've been on a bit of a triangle kick recently so here's another one. Clark's Triangle is a triangle where the leftmost entry of each row is 1 and the rightmost entries are made up of multiples of ...

Let us play a little golfing game. Given a single line of N space separated numbers from STDIN, one must output those numbers on N lines. So far, I came up with the three following bash solutions : ...

Note: Anders Kaseorg warns me that this could be a duplicate of another previous question. It seems so, and I'm sorry I did not find that question before posting this one. Nonetheless, that question ...

Given a positive integer, find its smallest positive integer multiple which is a run of 9 followed by an optional run of 0. In other words, find its smallest positive integer multiple which is matched ...

Pascal's Rhombus (which is actually a triangle) is obtained by adding in the pattern: * *** x instead of * * x This means that each cell is the sum of the three cells on the row directly ...

Getting the average of a list (e.g [2,6,7]) Get the length of the list: [2,6,7] -> 3 Sum the numbers in the list: 2 + 6 + 7 = 15. Divide the sum by their count: 15 / 3 = 5. You should compare ...

You must write code to print out your answer. The answer must include the following: Your code, byte count, name of language and the formatting style of my example (H1 header for bytecount/language ...

In this challenge, you are given two overlapping rectangles, and you need to calculate the rectangles created by removing one from the other. For example, if you remove the red rectangle from the ...

In golf, the standard scratch of a course is calculated using this formula: (3*num_of_3_par_holes + 4*num_of_4_par_holes + 5*num_of_5_par_holes) - difficulty_rating Your task is to calculate the ...

You might already be familiar with the game: Basketball FRVR in facebook. There are two types of score you can make: A virgin-shot:(we call it so in our country :D) When the ball enters the basket ...

Warm up: Regex, Paper, Scissors This is the challenge I originally wanted to post, before realising that some very short solution exist. Nevertheless, it can be an interesting problem to think about ...

Goal You are given an integer n (n > 1). You must output how many permutations of the integers 1 to n there are which start at 1, end at n, and don't have two consecutive integers which differ by ...

Continuing my It was just a bug challenge: Input: A string consisting of printable ASCII characters without white-spaces nor new-lines. Output: First turn the input into a palindrome by reverting ...

Compress a sparse matrix using Compressed sparse row (CSR, CRS or Yale format). These are all the same form of compression (ignore new Yale). Input may be any 2d data structure (list of lists, etc): ...

Warning: This challenge is only valid for languages with a compiler. Make a program (which is perfectly valid code) that outputs Hello, World, even before runtime. How? Let me explain. Many ...

How we can compare Waterfall VS Incremental VS Spiral VS ROD Software Development Model ? in following categories Planning in early stage Handle Large-Project Detailed Documentation Software House ...

Cyclic Polyglot Challenge This is the cops thread. You can find the robbers thread here. Cyclic Polyglot A N-element cyclic polyglot is a complete program that can be run in N different languages. ...

Cyclic Polyglot Challenge This is the robbers thread. You can find the cops thread here. Cyclic Polyglot A N-element cyclic polyglot is a complete program that can be run in N different languages. ...

Given an input string containing only alphanumeric ASCII characters and starting with a letter, swap each letter run with the digit run which follows. A run is a sequence of consecutive letters or ...

Given, in any way and order, dimensions (in whichever order you want) a probability (in whatever format you want) number of iterations (you may choose whether to count the initial state or not) do ...

NOTE: This question is different than Draw an ASCII Rectangle because the user has to input only 1 number to generate a box, unlike the other question, where the user has to input the x and y size of ...

A balanced string is a string of parentheses () so that every parenthesis is can be matched with another one. More rigorously they are the strings spanned by this grammar: S → (S)S | ε We can turn ...

Overview Given a list of digits, find the fewest operations to make 100 Input A string of digits, which may or may not be in numerical order. The order of the digits cannot be changed, however plus ...

You will be given a positive, whole number (that will never contain a 0) as input. Your task is to check whether it is a Lynch-Bell number or not. A number is a Lynch-Bell number if all of its digits ...

Program A outputs program B's code when run, and B outputs A's source. Requirements: Only one language across both programs Programs are different. One program that outputs itself does not qualify. ...

How can I create a search engine with php and xml database? (I want to use SimpleXMLElement() function).

The question is very simple: Given a number between 0 and 999999999 and output its length. Although it's simple, I'm looking specifically for a whole program written in C (and I will accept it). ...

Challenge: Given a square input matrix A, pad the matrix with one row and one column on all four sides. The value of each element in the top and bottom row should be the sum of the elements in each ...

The task is the following. Given an integer x (such that x modulo 100000000003 is not equal to 0) presented to your code in any way you find convenient, output another integer y < 100000000003 so ...

Given a string s and a positive integer N, gradually duplicate each character more and more until N duplicates, and then staying at N duplicates until N characters away from the end, then step down ...

Overview Given a 3 line string, figure out if the structure falls to the left, balances, or falls to the right. Input structure You can imagine the structure as metal rod with stuff on top, all ...

The Goldbach conjecture states that: every even number that is greater than 2 is the sum of two primes. We will consider a Goldbach partition of a number n to be a pair of two primes adding to n. ...

Given a positive integer as input, your task is to output a truthy value if the number is divisible by the double of the sum of its digits, and a falsy value otherwise (OEIS A134516). In other words: ...

Background Celebrating the release of Dyalog APL 16.0, where the solution to this problem is {⊢⌺(≢⍵)⊢⍵}Explanation Task Given a printable ASCII string of odd length n, make an n × n square with the ...

Write a function that calculates a row of the pascal triangle and returns the middle number, if there are 2 it should return their sum. Example: 5 would return 20 Example 2: 4 would return 6 ...

Write a program, that sends its own source code over network. Network example is TCP/UDP or web socket. Ethernet, Bluetooth, Wi-Fi and internet over USB are allowed. No need to write receiver ...

// example from: // https://msdn.microsoft.com/en-us/library/windows/desktop/ms737591(v=vs.85).aspx #define WIN32_LEAN_AND_MEAN #include <windows.h> #include <winsock2.h> #include <...

Inspired by the bugged output in @Carcigenicate's Clojure answer for the Print this diamond challenge. Print this exact text: 1 2 3 4 5 6 7 8 ...

This is a very very simple algorithm, that I am sure can be solved in many many different languages. In Spain ID cards (known as DNI) consist of 8 numbers and a control character. The control ...

Challenge Convert and print out a time in a 12-hour format. HH:MM AM/PM Examples Input: 'Fri Jun 30 2017 21:14:20 GMT-0700 (PDT)' 'Fri Jun 30 2017 00:10:23 GMT-0700 (PDT)' 'Fri Jun 30 2017 12:10:...