Cartesian product of two arrays

Question

How is it possible to do the Cartesian product using two arrays?

A={1,2,3}
B={2,3,4}
C={(1,2),(1,3),(1,4),(2,2),(2,3),(2,4),(3,2),(3,3),(3,4)}

This is the code I was using, but I always get a IndexOutOfBoundException.

public int[] cartesianProduct(int[] s1, int[] s2) {
    ArrayList<Integer> list = new ArrayList<>();
    for (int i = 0; i < s1.length; i++) {
        for (int v1 : s1) {
            for (int v2 : s2) {
                list.add(s1[i], s2[i]);
            }
        }
    }
    int[] result = new int[list.size()];
    int k = 0;
    for (int i : list) {
        result[k++] = i;
    }
    return result;
}

Answer 1

The elements of the output array should be pairs of integers, therefore an int array cannot be the type of the output, and you can't use a List<Integer> to collect the data.

One way to represent each pair of numbers is an int array of two elements. This way the output would be a 2D array, and the List used to collect the data can be a List<int[]>:

public int[][] cartesianProduct(int[] s1, int[] s2) {
    List<int[]> list = new ArrayList<>();
    for (int v1 : s1) {
        for (int v2 : s2) {
            list.add(new int[]{v1, v2});
        }
    }
    int[][] result = new int[list.size()][2];
    int k = 0;
    for (int[] i : list) {
        result[k++] = i;
    }
    return result;
}