题解 | #求1+2+3+...+n#巧用static成员

class Sum
{
public:
    Sum()
    {
        _ret+=_i;
        ++_i;
    }
    static int GetRet()
    {
        return _ret;
    }

private:
    static int _i;
    static int _ret;
};
    int Sum :: _i=1;
    int Sum :: _ret=0;


class Solution {
public:
    int Sum_Solution(int n) {
        Sum a[n];
        return Sum::GetRet();
    }
};