【Leetcode202】Happy Number

非常中規中矩的做法，沒有參考其他人怎麼做的，有時間看看

Runtime: 4 ms, faster than 68.02% of C++ online submissions for Happy Number.

Memory Usage: 7.4 MB, less than 100.00% of C++ online submissions for Happy Number. 

class Solution {
public:
    std::vector<int> results;
    bool isHappy(int n) {
        int s = pow2Num(n);
        if(s == 1)
            return true;
        else{
            if(isIncluded(s))
                return false;
            else{
                results.push_back(s);
                return isHappy(s);
            }
        }

    }
    int pow2Num(int m){
        int s = 0;
        while(m != 0){
            s += pow(m%10, 2);
            m /= 10;
        }
        return s;
    }
    bool isIncluded(int num){
        for(int index = 0; index < results.size(); ++index){
            if(results[index] == num)
                return true;
        }
        return false;
    }
};

 犯了一個比較低級的錯誤就是，把sqrt理解成平方的意思，實際上這是開平方！！！

我知道了sqrt是square root的縮寫