我想要输入一个大于100的n值得到pi的值

Question

Answer 1

#include<stdio.h>
int main(){
    int n,i,a=1;
    double p=-0,b;
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        b = a*1.0/(2*i-1);
        p = p + b;
        a = -a;
    }
    printf("%f",p*4);
}