HDU 3756 Dome of Circus

题目:http://acm.hdu.edu.cn/showproblem.php?pid=3756

三分,求包括所有给出点的最小圆锥的高和半径.说实话这道题还不怎么理解.

自己一直WA,主要是搜索时cal与三分的条件没写对.参考别人的代码A了.还得回来看.

#include <iostream>
#include <cmath>
using namespace std;

struct point
{
    double x;
    double y;
}p[10005];

int n;
double cal(double h)
{
    double R=0;  
    for(int i=0;i<n;i++)  
    {  
        //R=max(R,h*p[i].x/(h-p[i].y));  
        if(R*(h-p[i].y)<h*p[i].x)  
            R=h*p[i].x/(h-p[i].y);  
    }  
    return R;  
}

double binary_search(double left,double right)
{
    double mid ,midmid,R1,R2;
    while(fabs(right-left)>1e-8)
    {
        mid = (left+right)/2;
        midmid = (mid + right)/2;
        R1 = cal(mid);
        R2 = cal(midmid);
        if(mid*R1*R1>midmid*R2*R2)
        {
              left= mid;
        }else 
        {
            right = midmid;
        }
    }
    return mid; 
}
int main(int argc, const char *argv[])
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&n);
        double h = 0 , r = 0 ,Y;
        for(int i=0;i<n;i++)
        {
            double x,y,z;
            scanf("%lf%lf%lf",&x,&y,&p[i].y);
            p[i].x = sqrt(x*x +y*y); 
             Y=max(p[i].y,Y);  
        }
        r = binary_search(Y,1<<30);
        printf("%.3lf %.3lf\n",r,cal(r));
    }
    return 0;
}