Question

I’m using Ruby and needed to somehow generate all permutations of the digits in a given number and store them in an array. So for example I have number n = 9431, I need to generate all possible ways you can order those four numbers and store them in an array (The original can be in the array).

So if I input 9431 I need to get an array back with something like:

[9413, 9431, 9143, 9134, 9314, 9341, 4913, 4931, 4193, 4139, 4319, 4391, 1493, 1439, 1943, 1934, 1394, 1349, 3419, 3491, 3149, 3194, 3914, 3941]

Using strings is fine actually.

Clarification: Oh, and the output must be whole numbers in the array, not their individual digits.

Answer 1

This is “cheating”, because it uses intermediate strings which you didn’t want to do, but it works:

9431.to_s.chars.to_a.permutation.map(&:join).map(&:to_i).uniq
=> [9431, 9413, 9341, 9314, 9143, 9134, 4931, 4913, 4391, 4319, 4193, 
    4139, 3941, 3914, 3491, 3419, 3194, 3149, 1943, 1934, 1493, 1439, 
    1394, 1349]