Problem 11 El Pais

problem11

#!/usr/bin/ruby-1.9
require 'set'

class Problem11
  def self.solve(boxes, nails_per_box, weights)
    (1..nails_per_box).to_a.repeated_combination(boxes).select do |combination|
      weights.repeated_permutation(boxes).map do |weights|
        weights.zip(combination).map do |weight, value|
          weight * value
        end.inject(:+)
      end.to_set.size == 2**boxes 
    end.map(&:to_set)
  end
end

p Problem11.solve(5, 13, [5, 6])
#=> [#<Set: {3, 6, 11, 12, 13}>, #<Set: {6, 9, 11, 12, 13}>]