From: Mark Thomas <mark@...>
Date: 2009-05-18T22:10:07+09:00
Subject: Re: permute each element of a ragged array?

On May 17, 7:05 pm, Phlip <phlip2...@gmail.com> wrote:
> Rubies:
>
> Here's a programming chestnut. I suppose I could brute-force my way through
> this, but I'm curious if anyone knows a slick or clever way to do it.
>
> We are talking about returning an array of arrays, each containing each
> permutation of the elements in the input array of arrays, including no element:
>
>    def permute_sets(sets)
>      # ?
>    end
>
>    test 'permute sets' do
>      sets = [
>          %w( android hero ),
>          %w( insane clown posse ),
>          %w( phenomenauts ),
>        ]
>      permutations = permute_sets(sets)
>      assert permutations[ 0] == %w( android insane phenomenauts )
>      assert permutations[ 1] == %w( android insane )
>      assert permutations[ 2] == %w( android clown )
>      assert permutations[ 3] == %w( android posse )
>      assert permutations[ 4] == %w( hero insane phenomenauts )
>      assert permutations[-1] == []
>    end
>
> So, pass the test (generically, so any test with the same pattern would pass),
> and you win! Any ideas?
>
> --
>    Phlip

Why does your test not show %w{ android } ? Is the last set the only
one that can be nil?