Get a list of combinations of lists' elements

Question

Suppose I have 3 lists: [\'q\',\'w\'], [\'a\',\'s\'], [\'z\',\'x\']. How to get a list of possible combinations out of these lists? So I get a list [[\'q\',\'a\',\'z\'],[\'q

Answer 1

You might want to have a look at the class https://github.com/javagl/Combinatorics/blob/master/src/main/java/de/javagl/utils/math/combinatorics/MixedRangeCombinationIterable.java (a "standalone" class, just copy & insert into your project)

Example usage:

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Combinations
{
    public static void main(String[] args)
    {
        List> lists = new ArrayList>();
        lists.add(Arrays.asList('q','w'));
        lists.add(Arrays.asList('a','s'));
        lists.add(Arrays.asList('z','x'));

        MixedRangeCombinationIterable iterable = 
            new MixedRangeCombinationIterable(lists);
        for (List element : iterable)
        {
            System.out.println(element);
        }
    }
}

You are actually computing the elements of the http://en.wikipedia.org/wiki/Cartesian_product of the input sets