[恢]hdu 2529

2012-01-02 17:22:53

地址：http://acm.hdu.edu.cn/showproblem.php?pid=2529

题意：中文。

mark：设v的水平分量为x，则最终距离和x的关系应该是先增后减，遂三分。。。

代码：

# include <stdio.h>
# include <math.h>


double l, v ;


double f(double x)
{
    return sqrt(v*v-x*x)*l/x - 0.5*9.8*l*l/(x*x) ;
}


int main ()
{
    double left, right, m1, m2, h ;
    while (~scanf ("%lf%lf%lf", &h, &l, &v))
    {
        if (h == 0 && l == 0 && v == 0) break ;
        left = 0, right = v ;
        m1 = (left+right) / 3 ;
        m2 = (left+right)*2/3 ;
        while (right - left > 1e-5)
        {
            if (f(m1) < f(m2)) left = m1, m1 = m2, m2 = (m1+right)/2 ;
            else right = m2, m2 = m1, m1 = (m2+left)/2 ;
        }
        printf ("%.2lf\n", f(m1)+h) ;
    }
    return 0 ;
}