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)/;
             midmid=(mid+lef)/;
             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 ;
 }