Combine array of array into all possible combinations, forward only, in Ruby

Question

I have an array of arrays, like so:

[[\'1\',\'2\'],[\'a\',\'b\'],[\'x\',\'y\']]

I need to combine those arrays into a string containing all

Answer 1

Pure, reduce with product:

a = [['1','2'],['a','b'],['x','y']]
a.reduce() { |acc, n| acc.product(n).map(&:flatten) }.map(&:join)
#  => ["1ax", "1ay", "1bx", "1by", "2ax", "2ay", "2bx", "2by"]