题解 | 求1+2+3+...+n

class Sum
{
    public:
    Sum()
    {
        _i=_i+_a;
        _a++;
    }
    static int Get()
    {
        return _i;
    }
    private:
    static int _i;
    static int _a;

};
int Sum::_i=0; 
int Sum::_a=1;
class Solution {
public:
    int Sum_Solution(int n) {
        Sum a[n];
        return Sum::Get();
    }
};