Leetcode 202. Happy Number unordered_map()再用

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: 

Input: 19
Output: true
Explanation: 
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

题目链接：https://leetcode.com/problems/happy-number/

class Solution {
public:
    int fun(int n)
    {
        int res=0;
        while(n)
        {
            int t=n%10;
            res+=t*t;
            n=n/10;
        }
        return res;
    }
    bool isHappy(int n) {
        unordered_map<int,int> m;
        while(m[n]<2)
        {
            m[n]+=1;
            if(m[n]>1)
                return false;
            if(fun(n)==1)
                return true;
            n=fun(n);
        }
        return false;
    }
};