# All Questions

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### Is this a powerful number?

A powerful number is a positive integer $n$ such that for every prime $p$ that divides $n$, $p^2$ also divides $n$. Or equivalently, $n$ is powerful if and only if it can be written in the ...
3k views

### Chinese color mixing

Objective Given two Chinese ideographs meaning basic colors, output the ideograph that means the color resulting from mixing them. Basic colors The basic colors are: 靑(U+9751; blue) 赤(U+8D64; red) 黃(...
1 vote
176 views

### Most elegant one-liner to generate sqlite INSERTs

Challenge You find yourself in a bash terminal, and want to do some simple tests on sqlite3. So you issue the following command: ...
2k views

### Compute this fractal matrix

The unique-disjointness matrix ( UDISJ(n) ) is a matrix on all pairs of subsets of {1...,n} with entries  U_{(A,B)}=\begin{cases} 0, ~ if ~ |A\cap B|=1\\ 1, ~ ...
2k views

### Make a k-skip-j range

On the Mathematica Stack Exchange, 100xln2 asks: I need a list of integers […] The list contains integers and is characterized by [three] parameters, lets call them k and j [and listmax], which ...
3k views

### Meta-cat program

Write a program or function that takes input and outputs/returns a full program (in the same language) that outputs said input. Note that the input may contain any printable ASCII character or newline ...
956 views

### Continuously Count Consecutive Cases

Background Imagine that I'm creating a really long necklace, consisting of only two characters, A and B. You must count the ...
272 views

### Simulate Keyboard Inputs

Background You know how in text editors and just text fields in general, there's always that blinking bar where you type? Yeah, simulate typing there. You'll be given 3 inputs: The current text field, ...
790 views

### Compute the chromatic number of special graphs

This challenge is about computing the chromatic number of special types of graphs. Input The input will consist of two integers. A positive integer $n > 1$. A distance $d < n$. Task The ...
2k views

### Print all Polynomials

The set of all polynomials with integer coefficients is countable. This means that there is a sequence that contains each polynomial with integer coefficients exactly once. Your goal is it to write a ...
79 views

### Tips for golfing in Thue

Anyone got tips for golfing in Thue. One tip per answer, and no tips aplicable to all languages (like remove comments)
4k views

### "Print this diamond" gone beautifully wrong

Write a function (or a whole program) that outputs (or prints) the following ASCII art: Output: ...
2k views

### Generate the Crystal Maze™ time matrix

Behold! The Crystal Maze™ Time Matrix! ...
1 vote
152 views

### Start a program so that /proc/self/cmdline contains a binary representation of the input number

I am sorry for the very long description. But i think some information of how /proc/self/cmdline works and how it can be used to get a integer input was necessary. ...
1k views

### (Robbers) Fast and Golfiest Season 1: The Lord of the Strings

Fast and Golfiest Robbers Thread Welcome to the first season of Fast and Golfiest, a cops-and-robbers challenge! I designed this challenge to encourage competitive coding for efficiency (fastest ...
1k views

### (Cops) Fast and Golfiest Season 1: The Lord of the Strings

Fast and Golfiest Cops Thread Welcome to the first season of Fast and Golfiest, a cops-and-robbers challenge! I designed this challenge to encourage competitive coding for efficiency (fastest ...
3k views

### Code Golf for Golf

My first code golf question post! Hope u like it ;-) The task is simple. Write either an stdin-stdout program or a function. Input is a 2D array which contains only either characters or the integer <...
3k views

### Numbers that can be negated by reading backwards

Balanced ternary is a modified version of ternary (base 3), using the three digits 1,0 and -1...
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### Output / Convert to unary number

Your task is it to output a number as a unary string. You get the number of a non-negative integer input in the range of 0 - 2'000'000'000. Rules You can choose any character for the digit you like. ...
1 vote
470 views

### Relations between interval and semitones

Output this table: -2* -1* - 0 - 1 2 -1* 0 1 - 2 3 4 1 2 3 - 4 5 6 3 4 - 5 - 6 7 5 6 - 7 - 8 9 6 7 8 - 9 10 11 8 9 10 - 11 12 13 10 11 - 12 - 13 14 You can output one string with two types of ...
2k views

### Chamber of Reflection

Background A ray of light is fired from the top left vertex of an MxN Chamber, where M a denotes the width and ...
2k views

Diagonalize a vector into a matrix. Input A vector, list, array, etc. of integers $\mathbf{v}$ of length $n$. Output A $n \times n$ matrix, 2D array, etc. $A$ such that for each element $a_i \... 0 votes 1 answer 74 views ### Find the sum of primes [duplicate] Given a number x, find the sum of all primes up to that number. The input will always be a positive number, bigger than 2. An upper limit isn't defined, so data types can be ignored. Use whichever you ... 9 votes 13 answers 982 views ### Landmine Number V Background You have again x4 been given the task of calculating the number of landmines in a field. But this time, the field is not a number field... it's a field of letters. Our landmine letter ... 7 votes 1 answer 236 views ### Reverse Conway's Game of Life Conway's Game of Life is a cellular automaton "played" on an infinite grid, filled with cells that are either alive or dead. Once given an initial state, the board evolves indefinitely ... 10 votes 13 answers 1k views ### Landmine Number IV Background You have again x3 been given the task of calculating the number of landmines in a field. But this time, we have no landmine number, and some landmines have exploded. You must calculate the ... 14 votes 19 answers 2k views ### Vanilla Natural Logarithm Challenge There is a challenge for multiplying two numbers so I guess this counts too Given as input a positive real number n compute its natural logarithm. Your answer ... 6 votes 6 answers 955 views ### Critical Calculations Background In the game stick ranger, there is an item which grants the character the ability to get critical hits. Each time a projectile hits an enemy, it has some probability to be a critical hit (... 22 votes 40 answers 3k views ### Sum of a range of a sum of a range of a sum of a range of a sum of a range of a sum of Inspired by the fact that a few related challenges to this could be answered by Vyxal in 0 Bytes using a special flag combination. Given only one input integer$n$, calculate$f(n,n)$where  f(x,... 11 votes 14 answers 2k views ### Landmine Number III Background You have again, again been given the task of calculating the number of landmines in a field. But this time, the field is foggy. You must calculate the landmine score given a list/string of ... 11 votes 6 answers 690 views ### Compute the maximal Ducci period Given an initial$n$-tuple$t_0=(t_{0,1},...,t_{0,n})$, we can obtain its corresponding Ducci sequence$\{t_0, t_1, ...\}$by the recurrence$\displaystyle t_{i+1}=\left(\left|t_{i,1}-t_{i,2}\...
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Background You are planning your trip away from the Diamond City, and must travel through Diamond Road. However, Diamond Road branches away from Diamond City to different locations. Out of curiosity, ...
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### Landmine Number II

Background You have again been given the task of calculating the number of landmines in a field. However, we have now travelled into the flatlands. You must calculate the landmine score given a list/...
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### Landmine Number I

Background You have been given the task of calculating the number of landmines in a field. You must calculate the landmine score given a list/string of numbers and the landmine number. The landmine ...
685 views

A followup to this challenge by Jeremy Collprav, inspired by DLosc solving this in Regenerate. Some sections copied from the linked challenge. Linking chains We define a chain to be a string ...
1k views

Background We define the two types of chain to be a string that contains only dashes, "-", or only underscores, "_". We link two chains using one equals sign, "=". ...
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### Draw the initial positions of Mölkky pins in ASCII art

Write a function (or a whole program) that outputs (or prints) an ASCII art of the initial position of Mölkky pins. Output : ...
2k views

### Reversed Squares

Given an integer n, your task is to determine whether it is a perfect square that when reversed, is still a perfect square. You may assume n is always positive. When numbers such as 100 (10x10) are ...
847 views

### Translate the keitai input method

The keitai input method is a method for writing Japanese kana on a 12-key phone keypad. Similar to Western keypads, each kana is assigned to a key; when the key is pressed multiple times, it cycles ...
714 views

### Detect Maxima Using Persistent Homology

Inspired by this SO answer about peak detection. Background Persistent homology is a fancy term for a fancy math concept, but in this case all we care about is how it can be used for peak detection. ...
3k views

### Output each second

With roughly one second (plus or minus 10 ms) between outputs, output anything. The first output must be at most one second after the start of the program, but can be as soon as right when the program ...
1k views

### Approximate e using small numbers

Given an input integer from 1, 2, ..., n, the task to write code to make a number as close as possible (as measured by absolute distance) to e using only the four ...
218 views

### Minimum partition with non-empty intersections

Given a set of intervals $\mathcal{I} = \{I_1, \ldots, I_m\}$, where each interval $I_j$ is represented by its bounds $(a_j, b_j)$, find a partition $\mathcal{T}$ of $\mathcal{I}$ of minimal ...
2k views

### XOR of independent Bernoulli variables

In probability theory, a Bernoulli variable is a random variable which has a single parameter $p$, and is equal to 1 with probability $p$, and 0 with probability $1-p$. In this challenge, there ...
291 views

### Wrt "Hello World" prgrm bt wth n vwls

Create A "Hello, World!" program but without any vowels. Winner is the program with the least bytes. Rules: No vowels are allowed in the code. Must print to STDOUT Must be a full program. ...
198 views

### Tips for golfing in (,) in-paren-comma

What tips do you have for golfing in (,)? I've found that there are so many ways to make code shorter, and I want more ways. I doubt there even are any tips for (,) that are applicable in the majority ...
2k views

### Vertices of a regular dodecahedron

A regular dodecahedron is one of the five Platonic solids. It has 12 pentagonal faces, 20 vertices, and 30 edges. Your task is to output the vertex coordinates of a regular dodecahedron. The size, ...
1 vote
106 views

### Bunny Shakespeare poetry [closed]

Suppose you have a grid of cells that is 6 wide and arbitrarily tall. In each cell is a word. Let the bottom row, which is row #1, be the last 6 words of sample.txt in order. Let the second to last ...
280 views

### Crazyhouse chess KoTH

What is Crazyhouse Chess? Crazyhouse Chess is a chess variant that is basically normal chess except you can place a piece you previously captured back on the board instead of a regular turn. Bot ...