2.计算1/1-1/2+1/3-1/4+1/5 …… + 1/99 - 1/100 的值。

#include<stdio.h> 
#include<stdlib.h> 
int main()
{
 int  den = 1;  //分母 
 double member = 1.0;          //分子 
 double sum = 0.0;
 int flag = 1;
 for (int i = 0; i < 100; i++)
 {
  sum += flag * member / den;
  den++;
  flag *= -1;

 }
 printf("%lf\n", sum);
 system("pause");
 return 0;
}