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

思路：每个数总能转变成一个10以内的数，因此判断这个数是不是可以的就行了，10以内只有1和7是happy number，因此程序就很简单了

代码：

class Solution {
public:
    bool isHappy(int n) {
        vector<int> num;
        while(n>9){
            while(n){
                num.push_back(n%10);
                n/=10;
            }
            for(int e:num){
                n+=(e*e);
            }
            num.clear();
        }
        if(n==1||n==7)
        return true;
        else
        return false;
    }
};