计算1/2-2/3+3/4-…+19/20

#include <iostream>
using namespace std;
int main()  
{
	int i,sign=1,n=19;  
	double d,k;  
	i=1,k=0;  
	while(i<=n)  
	{ 
		d=double(i)/(i+1);  
		k=k+sign*d;  
		sign=-sign;  
		i++;  
	}  
	cout<<"k="<<k<<endl;  
	return 0;  
}