Happy Number

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example: 19 is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1

public class Solution {
    public boolean isHappy(int n) {
        if (n <= 0) {
            return false;
        }
        HashSet<Integer> set = new HashSet<Integer>();
        set.add(n);
        while (n != 1) {
            n = getNext(n);
            if (set.contains(n)) {
                return false;
            }
            set.add(n);
        }
        return true;
    }
 
    private int getNext(int n) {
        int ret = 0;
        while (n != 0) {
            ret += Math.pow(n % 10, 2);
            n /= 10;
        }
        return ret;
    }
}

==========

public class Solution {
    public boolean isHappy(int n) {
        int x = n;
        int y = n;
        while(x>1){
            x = cal(x) ;
            if(x==1) return true ;
            y = cal(cal(y));
            if(y==1) return true ;

            if(x==y) return false;
        }
        return true ;
    }
    public int cal(int n){
        int x = n;
        int s = 0;
        while(x>0){
            s = s+(x%10)*(x%10);
            x = x/10;
        }
        return s ;
    }
}