Generating all possible combinations from a List[List[Int]] in Scala

Question

Given the following list:

List(List(1,2,3), List(4,5))

I would like to generate all the possible combinations. Using yield, it

Answer 1

Feels like your problem can be described in terms of recursion:

If you have n lists of int: list1 of size m and list2, ... list n

• generate the X combinations for list2 to n (so n-1 lists)
• for each combination, you generate m new ones for each value of list1.
• the base case is a list of one list of int, you just split all the elements in singleton lists.

so with List(List(1,2), List(3), List(4, 5)) the result of your recursive call is List(List(3,4),List(3,5)) and for each you add 2 combinations: List(1,3,4), List(2,3,4), List(1,3,5), List(2,3,5).