BZOJ 1185 [HNOI2007]最小矩形覆盖 ——计算几何

程序写的太垃圾，卡不过去。

GG，甘拜下风。

#include <map>
#include <cmath>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define F(i,j,k) for (int i=j;i<=k;++i)
#define D(i,j,k) for (int i=j;i>=k;--i)
//#define double long double
#define eps 1e-8
#define ll long long
#define mp make_pair

struct Vector{
double x,y;
void print()
{
printf("Vector -> (%.3f,%.3f)\n",x,y);
}
};

struct Point{
double x,y;
void print()
{
printf("%.5f %.5f\n",x+eps,y+eps);
}
};

int n;

Vector operator - (Point a,Point b)
{Vector ret;ret.x=a.x-b.x;ret.y=a.y-b.y;return ret;}

Point operator + (Point a,Vector b)
{Point ret;ret.x=a.x+b.x;ret.y=a.y+b.y;return ret;}

Vector Vertical (Vector a)
{Vector ret;ret.x=-a.y;ret.y=a.x;return ret;}

double operator * (Vector a,Vector b)
{return a.x*b.y-a.y*b.x;}

Vector operator * (Vector a,double b)
{Vector ret;ret.x=a.x*b;ret.y=a.y*b;return ret;}

Point Node (Point P1,Vector V1,Point P2,Vector V2)
{return P1+V1*((V2*(P1-P2))/(V1*V2));}

Point a[50005];

void Test()
{
printf("Test : \n");
Point P1,P2;Vector V1,V2;
P1.x=0;P1.y=1;V1.x=1;V1.y=1;
P2.x=1;P2.y=0;V2.x=1;V2.y=2;
Node(P1,V1,P2,V2).print();
}

bool cmp(Point a,Point b)
{return fabs(a.x-b.x)<eps?a.y<b.y:a.x<b.x;}

Point sta[50005];
int top=0;

void Andrew()
{
sta[++top]=a[1];
F(i,2,n)
if (fabs(a[i].x-a[i-1].x)>=eps||fabs(a[i].y-a[i-1].y)>=eps){
while (top>=2&&(sta[top]-sta[top-1])*(a[i]-sta[top])<0) top--;
sta[++top]=a[i];
}
int lower=top;
D(i,n-1,1)
if (fabs(a[i].x-a[i+1].x)>=eps||fabs(a[i].y-a[i+1].y)>=eps){
while (top-lower>=1&&(sta[top]-sta[top-1])*(a[i]-sta[top])<0) top--;
sta[++top]=a[i];
}
}

double Dot(Vector a,Vector b)
{return a.x*b.x+a.y*b.y;}

double Len(Vector a)
{
return Dot(a,a);
}

void Finout()
{
freopen("in.txt","r",stdin);
}

Point now[4],ans[4];
double tmp=1e18,nowans;

void Rotating()
{
int l=top-1,r=3,p=2;
while (Dot(sta[2]-sta[1],sta[l]-sta[1])>Dot(sta[2]-sta[1],sta[l-1]-sta[1])) l--;
while (Dot(sta[2]-sta[1],sta[r]-sta[1])<Dot(sta[2]-sta[1],sta[r+1]-sta[1])) r++;
F(i,1,top-1)
{
while (Dot(sta[i+1]-sta[i],sta[l]-sta[i])>Dot(sta[i+1]-sta[i],sta[l+1]-sta[i])) l=l%top+1;
while (Dot(sta[i+1]-sta[i],sta[r]-sta[i])<Dot(sta[i+1]-sta[i],sta[r+1]-sta[i])) r=r%top+1;
while ((sta[i+1]-sta[i])*(sta
-sta[i])<(sta[i+1]-sta[i])*(sta[p+1]-sta[i])) p=p%top+1;
now[0]=Node(sta[i],sta[i+1]-sta[i],sta[l],Vertical(sta[i+1]-sta[i]));
now[1]=Node(sta[i],sta[i+1]-sta[i],sta[r],Vertical(sta[i+1]-sta[i]));
now[2]=Node(sta[p],sta[i+1]-sta[i],sta[r],Vertical(sta[i+1]-sta[i]));
now[3]=Node(sta[p],sta[i+1]-sta[i],sta[l],Vertical(sta[i+1]-sta[i]));
if ((nowans=sqrt(Len(now[0]-now[1])*Len(now[1]-now[2])))<tmp)
{
F(j,0,3) ans[j]=now[j];
tmp=nowans;
}
}
int st=-1;Point stp;
stp.x=1e18;stp.y=1e18;
F(i,0,3)
if (fabs(ans[i].y-stp.y)<eps?ans[i].x<stp.x:ans[i].y<stp.y)
st=i,stp=ans[i];
printf("%.5f\n",tmp+eps);
F(i,0,3) ans[(i+st)%4].print();
}

int main()
{
scanf("%d",&n);
F(i,1,n) scanf("%lf%lf",&a[i].x,&a[i].y);
sort(a+1,a+n+1,cmp);
Andrew();
Rotating();
}