一、题目

求1+2+3+...+n_牛客题霸_牛客网 

二、代码

1.使用静态成员变量+构造函数

class SUM
{
    private:
    static int _i;
    static int _ret;

    public:
    SUM()
    {
        _ret = _ret + _i;
        _i++;
    }

    static int GetRet()
    {
        return _ret;
    }
};
int SUM::_i=1;
int SUM::_ret=0;

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

2.使用内部类

class Solution {
    class SUM {
      public:
        SUM() {
            _ret = _ret + _i;
            _i++;
        }

        static int GetRet() {
            return _ret;
        }
    };

  public:
    int Sum_Solution(int n) {
        SUM s[n];
        return SUM::GetRet();
    }

  private:
    static int _i;
    static int _ret;
};

//类外定义
int Solution::_i = 1;
int Solution::_ret = 0;