hdu-4717-The Moving Points三分

http://acm.hdu.edu.cn/showproblem.php?pid=4717

画图得，最后的抛物线合并起来 去顶端部分。。。一定是  单峰函数。。所以三分。。

#include <iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<vector>
#include<queue>
#include<cmath>
using namespace std;
 double eps=1e-6;
 struct POINT
 {
    double x,y;
    POINT(double a=0,double b=0)
    {x=a,y=b;}
 };
 double dist(POINT p1,POINT p2)
 {
     return (  sqrt((p1.x-p2.x)*(p1.x-p2.x)+ (p1.y-p2.y)*(p1.y-p2.y) )   );
 }
 POINT point[310];
 POINT idx[310];
 double vx[310],vy[310];
 double ans;
 int n;
 double bin(double x)
 {
     int i,j;
     double maxx=0;

     for (i=1;i<=n;i++)
    {
        for(j=i+1;j<=n;j++)
        {
        double xx1=point[i].x+x*vx[i];
        double yy1=point[i].y+x*vy[i];

        double xx2=point[j].x+x*vx[j];
        double yy2=point[j].y+x*vy[j];

        double tmp=dist(POINT(xx1,yy1),POINT(xx2,yy2));
            if (tmp>maxx)
            maxx=tmp;
        }
    }
    if (maxx<ans) ans=maxx;
    return  maxx;
 }

int main()
{
    int t;
    cin>>t;int cnt=1;
    while(t--)
    {
        int i;
       cin>>n;
        for (i=1;i<=n;i++)
        {
            scanf("%lf%lf%lf%lf",&point[i].x,&point[i].y,&vx[i],&vy[i]);
        }
        double l=0;
        double r=1e16;
         ans=1e16;

        for (i=0;i<200;i++)
        {
            double m1=l+(r-l)/3;
            double m2=r-(r-l)/3;
            if (bin(m1)<bin(m2))
                r=m2;
            else l=m1;
        }

        printf("Case #%d: %.2lf %.2lf\n",cnt++,l,ans);


    }
    return 0;
}