leetcode 202 快乐数

class Solution {
public:
    bool isHappy(int n) {
        unordered_map<int,bool> m;
        while(n!=1){
            m[n]=true;
            int sum=0,a;
            while(n){
                a=n%10;
                sum+=a*a;
                n/=10;
            }
            n=sum;
            if(m[n]) return false;
        }
        return true;
    }
};