Return the cross product of a list of lists

Question

Given a list of size n, Write a program that returns all possible combination of elements contained in each list.

Example:

• List A = \"x, z\"

Answer 1

You do not need recursion. All you need to do is build up a set of intermediate solutions. Here is a non-recursive solution in Python:

# This does NOT use recursion!
def all_comb(list_of_lists):
    # We start with a list of just the empty set.
    answer = [[]]
    for list in list_of_lists:
        # new_answer will be the list of combinations including this one.
        new_answer = []
        # Build up the new answer.
        for thing in list:
            for prev_list in answer:
                new_answer.append(prev_list + [thing])
        # Replace the old answer with the new one.
        answer = new_answer
    # We now have all combinations of all lists.
    return answer

# Demonstration that it works.    
for comb in all_comb([["x", "y"], ["a", "b", "c"], ["o", "p"]]):
    print(" ".join(comb))