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

防止死循环， 加一个set存储这个值， 有重复的sum即break。

坑爹货 sum = n%10 * n%10 得到结果竟然不对。 必须要temp = n%10 ； sum = temp*temp;

运算符优先级的问题  sum =（ n%10） * （n%10）;