HDU2438 数学+三分

Turn the corner

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3070    Accepted Submission(s): 1232

Problem Description

Mr. West bought a new car! So he is travelling around the city.

One day he comes to a vertical corner. The street he is currently in has a width x, the street he wants to turn to has a width y. The car has a length l and a width d.

Can Mr. West go across the corner?

 

 

Input

Every line has four real numbers, x, y, l and w.
Proceed to the end of file.

 

 

Output

If he can go across the corner, print "yes". Print "no" otherwise.

 

 

Sample Input

10 6 13.5 4

10 6 14.5 4

 

 

Sample Output

yes no

 

 

Source

2008 Asia Harbin Regional Contest Online

代码：

//三分，左分因为最值在左边。
#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
double x,y,l,d;
double F(double m)
{
    return (x*sqrt(l*l-m*m)-m*y+m*sqrt(l*l-m*m))/l;
}
int main()
{
    while(scanf("%lf%lf%lf%lf",&x,&y,&l,&d)!=EOF)
    {
        double lef=-1.0*l,rig=0.0,mid,midmid;
        while(rig-lef>0.00000001)
        {
            mid=(lef+rig)/2;
            midmid=(mid+lef)/2;
            double tem1=F(mid);
            double tem2=F(midmid);
            if(tem1<=tem2) lef=midmid;
            else rig=mid;
        }
        if(d<=min(F(mid),F(midmid)))
        printf("yes\n");
        else printf("no\n");
    }
    return 0;
}