C++: 求1+2+3+...+n

int i = 1;
int sum = 0;
class Sum
{
public:
    Sum()
    {
        sum += i;
        ++i;
    }
};

class Solution {
public:
    int Sum_Solution(int n) {
        Sum a[n]; //调用n次sum的构造函数
        return sum;
    }
};