# All Questions

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### 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 ...
68 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 ...
251 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 ...
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 &...
1k views

80 views

### Shortest C program which compiles to largest file size [duplicate]

Challenge This challenge is to create the shortest C program which compiles to the largest file size. Your score for this challenge is ...
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 ...
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 ...
172 views

### Pristine Polyglots

As the title says, you are to create a pristine program in as many languages as possible. A pristine program, taken from here, is: Let's define a pristine program as a program that does not have any ...
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 ...
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://...

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