Colorful Number

Problem

A number can be broken into different sub-sequence parts. Suppose, a number 3245 can be broken into parts like 3 2 4 5 32 24 45 324 245. And this number is a colorful number, since product of every digit of a sub-sequence are different. That is, 3 2 4 5 (3*2)=6 (2*4)=8 (4*5)=20 (3*2*4)= 24 (2*4*5)= 40
But 326 is not a colorful number as it generates 3 2 6 (3*2)=6 (2*6)=12.
You have to write a function that tells if the given number is a colorful number or not.

Solution

public static boolean colorfulNumber(int num) {
    //if(num == null) return false;

    //convert num to arraylist
    List<Integer> al = new ArrayList<Integer>();
    while(num > 0) {
        al.add(num%10);
        num /= 10;
    }
    System.out.println(al);
    
    //store res into hashset
    Set<Integer> hs = new HashSet<Integer>();
    for(int i=1; i<al.size(); i++) {
        for(int j=0; j<al.size()-i+1; j++) {
            int pro = al.get(j);
            for(int k=j+1; k<j+i; k++) {
                pro = pro * al.get(k);
            }
            System.out.println(pro);
            if(hs.contains(pro)) return false;
            else hs.add(pro);
        }
    }
    System.out.println(hs);
    return true;
}