From: Mark Thomas <mark@...>
Date: 2009-05-18T23:35:07+09:00
Subject: Re: permute each element of a ragged array?

Not sure why the test must be as written, because the order doesn't
fall in a logical pattern (as far as I can tell). Here's one that
returns all the correct answers, but not in the prescribed order:

def permute_sets(sets)
  return [sets, ""] if sets.size < 2
  items = sets.shift << ""
  balance = permute_sets(sets)
  output = []
  items.each do |item|
    balance.each do |bal|
      output << "#{item} #{bal}".strip
    end
  end
  return output
end

Output:
android insane phenomenauts
android insane
android clown phenomenauts
android clown
android posse phenomenauts
android posse
android phenomenauts
android
hero insane phenomenauts
hero insane
hero clown phenomenauts
hero clown
hero posse phenomenauts
hero posse
hero phenomenauts
hero
insane phenomenauts
insane
clown phenomenauts
clown
posse phenomenauts
posse
phenomenauts


(The last line is the empty string)