Cartesian product of two arrays

arrays, cartesian-product, exception, java

Solution

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;
}

Problem

Original source