思路{
先求凸包,发现矩形的一条边一定与凸多边形的一条边重合.
用类似旋转卡壳的方式即可求出对于这条边为底,最左端的点,最右端的点,最远的点,
这样直接更新答案就可以了.
}
#include<bits/stdc++.h> #define RG register #define il inline #define N 50010 #define db double using namespace std; #define eps (1e-8) db Ans=1e60; struct point{ db x,y; point() {} point (db X,db Y):x(X),y(Y) {} bool operator <(const point & a)const{return (fabs(y-a.y)<eps)?x<a.x:y<a.y;} point operator +(const point & a)const{return point(x+a.x,y+a.y);} point operator -(const point & a)const {return point(x-a.x,y-a.y);} point operator *(const db & k)const{return point(k*x,k*y);} db operator *(const point & a)const{return x*a.y-y*a.x;} db operator ^(const point & a)const{return x*a.x+y*a.y;} db len(){return sqrt(x*x+y*y);} }p[N],st[N],q[4]; int n,top; int cmp(db k){if(fabs(k)<eps)return 0;return k>0?1:-1;} bool comp(const point & a,const point & b){return cmp(b.x-a.x)?a.x<b.x:a.y<b.y;} void Graham(){ sort(p+1,p+n+1,comp); for(int i=1;i<=n;++i){ while(top>1&&(st[top]-st[top-1])*(p[i]-st[top-1])<eps)top--; st[++top]=p[i]; }int NN=top;st[++top]=p[n-1]; for(int i=n-2;i>1;i--){ while(top>NN&&(st[top]-st[top-1])*(p[i]-st[top-1])<eps)top--; st[++top]=p[i]; }n=top; for(int i=1;i<=top;++i)p[i]=st[i],p[0]=st[top]; } void RC(){ int l(1),r(1),u(1); db L,R,H,d; for(int i=0;i<top;++i){ d=(p[i+1]-p[i]).len(); while((p[i+1]-p[i])*(p[u+1]-p[i])-(p[i+1]-p[i])*(p[u]-p[i])>-eps)u=(u+1)%n; while(((p[r+1]-p[i])^(p[i+1]-p[i]))-((p[r]-p[i])^(p[i+1]-p[i]))>-eps)r=(r+1)%n; if(!i)l=r; while(((p[l+1]-p[i])^(p[i+1]-p[i]))-((p[l]-p[i])^(p[i+1]-p[i]))<eps)l=(l+1)%n; L=((p[l]-p[i])^(p[i+1]-p[i]))/d; R=((p[r]-p[i])^(p[i+1]-p[i]))/d; H=((p[i+1]-p[i])*(p[u]-p[i]))/d; if(H<0)H=-H; db tmp=(R-L)*H; if(tmp<Ans){ Ans=tmp; q[0]=p[i]+(p[i+1]-p[i])*(R/d); q[1]=q[0]+(p[r]-q[0])*(H/(q[0]-p[r]).len()); q[2]=q[1]-(q[0]-p[i])*((R-L)/(p[i]-q[0]).len()); q[3]=q[2]-(q[1]-q[0]); } } } int main(){ scanf("%d",&n); for(int i=1;i<=n;++i)scanf("%lf%lf",&p[i].x,&p[i].y); Graham();RC();printf("%.5lf\n",Ans); int s(0); for(int i=1;i<=3;++i)if(q[i]<q[s])s=i; for(int i=0;i<=3;++i){ printf("%.5lf %.5lf\n",q[(i+s)%4].x,q[(i+s)%4].y); } return 0; }