Happy Number

Happy Number

问题：

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.

思路：

　　hashset

我的代码：

public class Solution {
    public boolean isHappy(int n) {
        HashSet<Long> hs = new HashSet<Long>();
        long num = n;
        while(!hs.contains(num))
        {
            if(num == 1) return true;
            hs.add(num);
            long tmp = 0;
            while(num != 0)
            {
                long remain = num%10;
                tmp += remain * remain;
                num /= 10; 
            }
            num = tmp;
        }
        return false;
    }
}