LeetCode Happy Number

Description:

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

Solution:

默认了一个条件：所有的数字，将他的各个位数平方和带入的循环，是一个有限循环。

import java.util.*;

public class Solution {
public boolean isHappy(int n) {
HashSet<Integer> set = new HashSet<Integer>();
set.add(n);

int temp = 0, ones;
while (true) {
temp = 0;
while (n > 0) {
ones = n % 10;
n /= 10;
temp += ones * ones;
}

n = temp;
if (n == 1)
return true;
if (set.contains(n))
break;
set.add(n);
}

return false;
}
}