Happy Number

Source

• leetcode: 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

java

public class Solution {
    public boolean isHappy(int n) {
        Set set = new HashSet();
        while(set.add(n)){
            int result=0;
            while(n!=0){
                result += Math.pow(n%10, 2);
                n/=10;
            }
            if(result==1) return true;
            n = result;
        }
        return false;
    }
}