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

Credits:

Special thanks to @mithmatt and @ts for
adding this problem and creating all test cases.

解题思路：建立一个vector，里面装得是新生成的数字，如例子中的19，82，68，100，每次产生一个新的数字就到这个vector中查询是否已经存在，如果已经存在，则必定会陷入循环；如果不存在，则加入到vector，继续生成新的数字。

class Solution {
public:
    vector<int> vec;
    bool isHappy(int n) {
       if(n==1) return true;
       vector<int>::iterator it=find(vec.begin(),vec.end(),n);
       if(it==vec.end()){//在vector中没有找到该数字。
           vec.push_back(n);
           int total=0;
           while(n){
               total+=(n%10)*(n%10);
               n/=10;
           }
           return isHappy(total);
       }else{
           return false;
       }
    }
};