LeetCode_202. Happy Number

202. Happy Number

Easy

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:

Input: 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

package leetcode.easy;

public class HappyNumber {
	public boolean isHappy(int n) {
		if (n == 0) {
			return false;
		}
		while (n != 1) {
			int n2 = n;
			n = 0;
			while (n2 > 0) {
				n += (n2 % 10) * (n2 % 10);
				n2 /= 10;
			}
			if (n == 4) {
				return false;
			}
		}
		return true;
	}

	@org.junit.Test
	public void test() {
		System.out.println(isHappy(19));
	}
}