求解1/1-1/2+1/3-.....+1/99-1/100

#include
int main()
{
  int num = 1;
  int flag = 1;
  double sum = 0.0;
  for (num = 1; num <= 100; num++)
  {
    sum += flag * (1.0 / num);
    flag = -flag;
  }
  printf("%lf\n", sum);
  return 0;
  }