输出是空的，我又不会了，想计算圆周率

Question

Answer 1

改好的代码如下

#include<stdio.h>
#include<math.h>
int main(void)
{
    int n;
    double i, a, pi1;
    n = 1;
    a = 0;
    i = 1;
    do
    {
        a = a - pow(-1,n)*i;
        n = n + 1;
        i = 1/(2 * (double)n - 1);
    } while (i > 1e-4);
    pi1 = 4 * a;
    printf("圆周率的近似值为%.12f\n",pi1);
    return 0;
}