怎么弄123456789

#include <stdio.h>
int main()
{
    int a = 1;
    float s = 0;
    float t = 0;
    int i;
    for (i=1;;i++)
    {
        t = 1.0/(2*i-1);
        if(t < 0.00001)
            break;
        s += a*t;
        a = -a;
    }
    printf("%.4f",s);
    return 0;
}

供参考：

#include <stdio.h>
#include <math.h>
int main()
{
    int i = 1, k = 1;
    double s = 0, t = 1.0;
    while (fabs(t) >= 1e-5)
    {
        t = 1.0 * k / (2 * i - 1);
        s += t;
        k = -k;
        i++;
    }
    printf("s=%.4f\n", s);
    return 0;
}