[Niuke] find 1+2+3+... +n

seek 1+2+3+...+n_ Niuke Tiba _ Cattle from (nowcoder.com)

subject ：

seek 1+2+3+...+n, It is required that multiplication and division shall not be used 、for、while、if、else、switch、case Wait for keywords and conditional statements （A?B:C）.

Data range ： 0<n≤200
Advanced ： Spatial complexity O(1) , Time complexity  O(n)

Ideas ：

make the best of C++ characteristic , The construction object constructor will be called automatically , Let the summation be done in the constructor

Code ：

class sum
{
public:
    sum()
    {
        _sum+=_i;
        _i++;
    }
    static int get_sum()
    {
        return _sum;
    }
private:    
    int static _i;
    int static _sum;
};
class Solution {
public:
    int Sum_Solution(int n) 
    {
        sum arr[n];
        return sum::get_sum();
    }
};
int sum:: _i = 1;
int sum:: _sum = 0;