求圆周率的近似值 C++

#include<iostream>
#include<cmath>
using namespace std;
int main() 
{ 
	double sum=0,solo=1;
	int i=1;
	while(fabs(i/solo)>1e-8)
	{
		sum=sum+i/solo;
		solo=solo+2;
		i=-i;
	}
	cout<<4*sum;
}