Given an array of N numbers select all the possible groups of size 1..N that may be selected

combinations_calculator.rb

def word_combinations(words, original_set_size = words.count, start_index = 0, end_index = words.count - 1, combinations = 1)

  words[start_index..end_index].each do |combination|
    words[0..original_set_size - 1].each do |original_combination|
      unless combination.include?(original_combination.first)
        new_combination = (combination + original_combination).sort

        unless words.include?(new_combination)
          words << new_combination
        end
      end
    end
  end

  combinations += 1

  return words if combinations == original_set_size

  word_combinations(words, original_set_size, end_index + 1, words.count - 1, combinations)
end

pp word_combinations [['uno'], ['dos'], ['tres']]