Iterative Cartesian Product in Java

Question

I want to compute the cartesian product of an arbitrary number of nonempty sets in Java.

I\'ve wrote that iterative code...

public s         


        

Answer 1

I wrote an recursive cartesian product algorithm for table of Strings. You can modify it to have sets istead. Below is the algorithm. It's also explained in my article

public class Main {

public static void main(String[] args) {
    String[] A = new String[]{ "a1", "a2", "a3" };
    String[] B = new String[]{ "b1", "b2", "b3" };
    String[] C = new String[]{ "c1" };

    String[] cp = CartesianProduct(0, A, B, C);

    for(String s : cp) {
         System.out.println(s);
    }
}

public static String[] CartesianProduct(int prodLevel, String[] res, String[] ...s) {
    if(prodLevel < s.length) {
        int cProdLen = res.length * s[prodLevel].length;
        String[] tmpRes = new String[cProdLen];

        for (int i = 0; i < res.length; i++) {
            for (int j = 0; j < s[prodLevel].length; j++) {
                tmpRes[i * res.length + j] = res[i] + s[prodLevel][j];
            }
        }
        res = Main.CartesianProduct(prodLevel + 1, tmpRes, s);
    }
    return res;
}}