From: Rick DeNatale <rick.denatale@...>
Date: 2009-05-18T09:39:23+09:00
Subject: Re: permute each element of a ragged array?

On Sun, May 17, 2009 at 7:10 PM, Phlip <phlip2005@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?

I can't say I understand the pattern what about
%w(android clown phenomenauts)
%w(android posse phenomenauts)

Would they be in the sequence? Does order matter, what about
permutations[5] etc.



-- 
Rick DeNatale

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