Create all permutations of an array of an array.

Example

comb([[3], ['a', 'c', 'f'], [4,6], [5,9]])
=> ["3a45", "3a49", "3a65", "3a69", "3c45", "3c49", "3c65", "3c69", "3f45", "3f49", "3f65", "3f69"]

gistfile1.rb

  def comb(arr) 
    head = arr[0]
    if arr[1..-1].present?
      results = []

      head.each{|x|
        comb(arr[1..-1]).each{|s|
          results << "#{x}#{s}" # Adjust concatentation to suit your types.
        }
      }

      return results
    else
      head
    end
  end

gistfile2.txt

# Then I discovered Array#product. D'oh!
def comb(arr) 
  arr.first.product(*arr[1..-1]).map(&:join)
end