【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

import java.util.HashSet;
import java.util.Set;

class Solution {
	public static boolean isHappy(int n) {
		if (n < 1) {
			return false;
		}
		if (n == 1) {
			return true;
		}
		Set<Integer> showNums = new HashSet<Integer>();
		showNums.add(n);
		while (true) {
			int sum = 0;
			while (n != 0) {
				int oneDigital = n % 10;
				n = n / 10;
				sum = sum + oneDigital * oneDigital;
			}
			if (sum == 1) {
				return true;
			} else {
				if (showNums.contains(sum)) {
					return false;
				} else {
					showNums.add(sum);
				}
			}
			n = sum;
		}
	}
}