How to get all the possible combinations of multiple lists?

Question

I have multiple lists like so (Can be in any length and number):

['a1', 'a2']
['b1', 'b2', 'b3']

I can't figure out how to get all the possible combinations of these lists, wanted result:

[
  ['a1', 'b1'],
  ['a1', 'b2'],
  ['a1', 'b3'],
  ['a2', 'b1'],
  ['a2', 'b2'],
  ['a2', 'b3']
]

Does anyone have a suggestion for this (any language is fine)? I tried it using recursion but with no luck.

In python: https://stackoverflow.com/questions/44176008/how-to-get-all-combination-from-multiple-lists — Nick, Feb 06 '21 at 07:42
`[[a, b] for a in ['a1', 'a2'] for b in ['b1', 'b2', 'b3']]` — Samwise, Feb 06 '21 at 07:43
Does this answer your question? [How to get all combination from multiple lists?](https://stackoverflow.com/questions/44176008/how-to-get-all-combination-from-multiple-lists) — Epsi95, Feb 06 '21 at 07:48
preferably in javascript, but I need an algorithm to work with, not something like python's ```itertools``` — Two Horses, Feb 06 '21 at 07:49
@Anonymous But cartesian product are for sets of pairs, doesn't really apply here I think — Two Horses, Feb 06 '21 at 07:54
If you look at the doc for `itertools`, it's actually really good about explaining the algorithms behind the functions, and even provides example implementations of most of the functions. — Samwise, Feb 06 '21 at 15:50

score -3 · Answer 1 · answered Feb 06 '21 at 07:49

If I understand you correctly ( I'm not sure) but in java you should use Set to eliminate duplicates, then:

    List<String> list = Arrays.asList("a1", "a2");

    List<String> anotherList = Arrays.asList("b1", "b2", "b3");

    Set<String> set = new HashSet<>(list);
    Set<String> anotherSet = new HashSet<>(anotherList);

    set.stream()
        .forEach(setElement -> anotherSet.stream()
            .forEach(anotherSetElement -> System.out.println(setElement + " " + anotherSetElement)));

That works for 2 arrays, but I could have any number of arrays — Two Horses, Feb 06 '21 at 07:52

How to get all the possible combinations of multiple lists?

1 Answers1