p3.c

好东西,绝对是好东西,我向大家推荐

#include<math.h>
int main()
{
	int i,j,n,N;
	double pi;
	for(i=0; ;i++)
	{	
		pi=0;
		scanf("%d",&N);
	        if(N==0)
		{
			break;
		}
		for(n=3; ;n=n+2)
		{
			if((1.0/n<=pow(10,-N))&&(1.0/(n-2)>pow(10,-N)))
			{	
			        break;
			}
		}
		for(j=3;j<=n;j=j+4)
		{
			pi=pi+1.0/(j-2)-1.0/j;
		}
		switch(N)
		{
			case 2:printf("%.2f\n",4*pi);break;
		        case 3:printf("%.3f\n",4*pi);break;
		        case 4:printf("%.4f\n",4*pi);break;
		        case 5:printf("%.5f\n",4*pi);break;
		        case 6:printf("%.6f\n",4*pi);break;		
		}
		
	}
return 0;	
}