hdu 3694 10 福州 现场 E - Fermat Point in Quadrangle

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;

const double eps=1e-10;

double add(double a,double b)
{
	if(abs(a+b)<eps*(abs(a)+abs(b))) return 0;
	return a+b;
}

struct point
{
    double x,y;
    point () {}
    point (double x,double y) : x(x),y(y){ }
    point operator + (point p)
    {
    	return point (add(x,p.x),add(y,p.y));
    }
    point operator - (point p)
    {
    	return point (add(x,-p.x),add(y,-p.y));
    }
    point operator * (double d)
    {
    	return point (x*d,y*d);
    }
    double dot(point p)
    {
    	return add(x*p.x,y*p.y);
    }
    double det(point p)
    {
    	return add(x*p.y,-y*p.x);
    }
};

bool on_seg(point p1,point p2,point q)
{
	return (p1-q).det(p2-q)==0&&(p1-q).dot(p2-q)<=0;
}

point intersection(point p1,point p2,point q1,point q2)
{
	return p1+(p2-p1)*((q2-q1).det(q1-p1)/(q2-q1).det(p2-p1));
}

bool cmp_x(const point&p,const point& q)
{
	if(p.x!=q.x) return p.x<q.x;
	return p.y<q.y;
}

vector<point> convex_hull(point*ps,int n)
{
	sort(ps,ps+n,cmp_x);
	//for(int i=0;i<n;i++) printf("x=%.f %.f")
	int k=0;
	vector<point> qs(n*2);
	for(int i=0;i<n;i++){
		while(k>1&&(qs[k-1]-qs[k-2]).det(ps[i]-qs[k-1])<=0) k--;
		qs[k++]=ps[i];
	}
	for(int i=n-2,t=k;i>=0;i--){
		while(k>t&&(qs[k-1]-qs[k-2]).det(ps[i]-qs[k-1])<=0) k--;
		qs[k++]=ps[i];
	}
	qs.resize(k-1);
	return qs;
}

double dis(point p1,point p2)
{
    return sqrt((p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y));
}
bool equ(point p1,point p2)
{
    if(fabs(p1.x-p2.x)<eps&&fabs(p1.y-p2.y)<eps)
        return true;
    return false;
}
int main()
{
    point p[10];
    for(int i=0;i<4;i++)
        scanf("%lf%lf",&p[i].x,&p[i].y);
    while(p[0].x!=-1&&p[0].y!=-1)
    {
        vector <point> m;
        double minn=100000000,d;
        m=convex_hull(p,4);
        if(m.size()==4)
            minn=dis(m[1],m[3])+dis(m[0],m[2]);
        for(int i=0;i<4;i++)
        {
            d=0;
            for(int j=0;j<4;j++)
                d+=dis(p[i],p[j]);
            minn=min(minn,d);
        }
        printf("%.4f\n",minn);
        for(int i=0;i<4;i++)
            scanf("%lf%lf",&p[i].x,&p[i].y);
    }
    return 0;
}