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
题目含义：对任意一个正整数，求每个数位上数字的平方并加和后得出新的正整数，循环此过程若最终收敛为1，则该数字为happy number，否则程序可能从某个数开始陷入循环。
1 public boolean isHappy(int n) { 2 if (n < 1) return false; 3 HashSet<Integer> set = new HashSet<>(32);// 用于保存中间出现的结果 4 set.add(1); 5 int tmp; 6 int newN; 7 // n的值不能重复出现，否则会死循环 8 while (!set.contains(n)) { 9 set.add(n); 10 newN = 0; 11 while (n > 0) { 12 tmp = n % 10; 13 n /= 10; 14 newN += tmp * tmp; 15 } 16 n = newN; 17 } 18 return n == 1; 19 }