#include <iostream>

using namespace std;

class Plus

{

 public:

    Plus() { ++i, sum += i; }

    //去掉以下的reset函数试试

    static void reset() { i = 0; sum = 0; }

    //去掉以下的statickeyword试试

    static int getSum() { return sum; } 

private:

   static int i;

   static int sum;

}; 

int Plus::i = 0;

int Plus::sum = 0; 

int cacSum(int n)

 {

    //仅仅有static函数才干如此调用

    Plus::reset();  

     Plus *test = new Plus[n];

    delete[] test; 

    return Plus::getSum();

 } 

 int main()

 {

    int i = 100;

    int result = cacSum(i);

    cout << "result = " << result << endl;

	system("pause");

	return 0;

 }

方法2

int getSum(int n)

 {

	 int result=0;

	 (n>0)&&(result=getSum(n-1)+n);

	 return result;

 }