求圆周率

void main()
{ 
   double sum=0;
   for(int i=0;;i++)
   {
       double term=1.0/(2*i+1);
           if(i%2==0)
               sum=sum+term;
           else
               sum=sum-term;
           if(term<1e-6)break;

   }
   printf("%.2f",sum);
} 

#include<stdio.h>

void main()
{ 
   double sum=0;
   int flag=1;
   int a=0;
   double term=1.0/(2*a+1);
   while(term>1e-6)
   {
       term=1.0/(2*a+1);
       sum=sum+term*flag;
       a++;
       flag=-flag;
   }
   printf("%.2f",sum);
}