求π时的最小迭代步骤

Question

 

Answer 1

#include <stdio.h>
#include <math.h>
double fun(int n)
{
    double pi = 0;
    int f = 1;
    for(int i=1;i<2*n;i+=2)
    {
        pi += 1.0*f/i;
        f *= -1;
    }
    return 4*pi;
}
void main()
{
    double d;
    scanf("%lf",&d);
    int n=2;
	double f = 1;
	double l = fun(2);
    while(f > d)
	{
		n++;
		double b = fun(n);
		f = fabs(b-l);
        l=b;
	}
    printf("最小迭代步骤:%d次",n-1);
}