From: Rick DeNatale <rick.denatale@...>
Date: 2009-05-18T23:52:22+09:00
Subject: Re: permute each element of a ragged array?

On Mon, May 18, 2009 at 10:35 AM, Mark Thomas <mark@thomaszone.com> wrote:
> 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).

Exactly, I don't see a general way to see a pattern when the
assertions are expressed as indexed elements equaling specific values.

Here's another 'solution'

def permute_sets(sets, selected=[])
   if sets.empty?
     selected << []
   else
     sub_permutations = permute_sets(sets[1..-1])
     sub_permutations.each do |sub_permutation|
       sets.first.each do |selection|
         selected << [selection] + sub_permutation
       end
       selected << sub_permutation
     end
   end
   selected
 end

 def assert(perms, i, value)
   if perms[i] == value
     puts "permutations[#{i}] passes"
   else
     puts "permutations[#{i}] fails"
     if perms.include?(value)
       puts " but #{value.inspect} IS included in the list of permutations!"
     end
   end
 end

   sets = [
       %w( android hero ),
       %w( insane clown posse ),
       %w( phenomenauts ),
     ]
   permutations = permute_sets(sets)

   permutations.each do |p|
     p p
   end

   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, []

Which produces the output:

["android", "insane", "phenomenauts"]
["hero", "insane", "phenomenauts"]
["insane", "phenomenauts"]
["android", "clown", "phenomenauts"]
["hero", "clown", "phenomenauts"]
["clown", "phenomenauts"]
["android", "posse", "phenomenauts"]
["hero", "posse", "phenomenauts"]
["posse", "phenomenauts"]
["android", "phenomenauts"]
["hero", "phenomenauts"]
["phenomenauts"]
["android", "insane"]
["hero", "insane"]
["insane"]
["android", "clown"]
["hero", "clown"]
["clown"]
["android", "posse"]
["hero", "posse"]
["posse"]
["android"]
["hero"]
[]
permutations[0] passes
permutations[1] fails
 but ["android", "insane"] IS included in the list of permutations!
permutations[2] fails
 but ["android", "clown"] IS included in the list of permutations!
permutations[3] fails
 but ["android", "posse"] IS included in the list of permutations!
permutations[4] fails
 but ["hero", "insane", "phenomenauts"] IS included in the list of permutations!
permutations[-1] passes


-- 
Rick DeNatale

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