package normal;

import java.util.HashSet;

/**

* @program JavaBooks

* @description: 202.快乐数

* @author: mf

* @create: 2019/11/06 10:15

*/

public class IsHappy {

public static void main(String[] args) {

System.out.println(isHappy(19));

System.out.println(isHappy2(19));

}

/**

* 递归，但有4的话，就一直循环，所以是4就false

* @param n

* @return

*/

private static boolean isHappy(int n) {

if (n == 1) return true;

if (n != 4) {

int sum = 0, k = n;

while (k > 0) {

sum += (k % 10) * (k % 10);

k /= 10;

}

return isHappy(sum);

}

return false;

}

private static boolean isHappy2(int n) {

if (n == 1) return true;

HashSet<Integer> set = new HashSet<>();

while (2 > 1) {

int sum = 0;

while (n > 0) {

sum += (n % 10) * (n % 10);

n /= 10;

}

if (sum == 1) return true;

if (!set.add(sum)) return false;

n = sum;

}

}

}