void main()
{
int n=0
double i=1
double sum=0
while((1/i)>0.0000001)
{
n++
if(n%2==0) i=i*(-1)
sum=sum+1.0/i
if(i<0) i=i*(-1)
i+=2
}
printf("%lf",sum*4)
}
//刚少了项数
#include "stdio.h"
void main()
{
int n=0
double i=1
double sum=0
while((1/i)>0.0000001)
{
n++
if(n%2==0) i=i*(-1)
sum=sum+1.0/i
if(i<0) i=i*(-1)
i+=2
}
printf("%lf,项数为%d",sum*4,n)
}
#include <stdio.h>int main()
{
float f
double pi,i,sign
while(scanf("%f",&f)==1)
{
pi=0
i=1
sign=1
do
{
pi+=sign*1.0/i
}while(1.0/i>=f&&(sign=-sign)&&(i+=2))
printf("%lf\n",pi*4.0)
}
return 0
}
