BZOJ 1185: [HNOI2007]最小矩形覆盖-旋转卡壳法求点集最小外接矩形(面积)并输出四个顶点坐标-备忘板子

来源:旋转卡壳法求点集最小外接矩形（面积）并输出四个顶点坐标

BZOJ又崩了，直接贴一下人家的代码。

代码:

 #include"stdio.h"
 #include"string.h"
 #include"math.h"
 #define M 50006
 #define eps 1e-10
 #include"stdlib.h"
 #define inf 999999999
 typedef struct node
 {
     double x,y,dis,cos;
 }P;
 P p[M],q[M],pp[M];
 double min(double a,double b)
 {
     return a<b?a:b;
 }
 int cmp(const void *a,const void *b)
 {
     if(fabs((*(struct node*)a).cos-(*(struct node*)b).cos)<eps)
         return (*(struct node*)a).dis>(*(struct node*)b).dis?:-;
     else
         return (*(struct node*)b).cos>(*(struct node*)a).cos?:-;

 }
 double pow(double x)
 {
     return x*x;
 }
 double Len(node p0,node p1)
 {
     return pow(p1.x-p0.x)+pow(p1.y-p0.y);
 }
 double COS(node p0,node p1)
 {
     double x1=p1.x-p0.x;
     double y1=p1.y-p0.y;
     double x2=;
     double y2=;
     return (x1*x2+y1*y2)/sqrt((x1*x1+y1*y1)*(x2*x2+y2*y2));
 }
 double cross(node p0,node p1,node p2)
 {
     double x1=p1.x-p0.x;
     double y1=p1.y-p0.y;
     double x2=p2.x-p0.x;
     double y2=p2.y-p0.y;
     return x1*y2-x2*y1;
 }
 double dot(node p0,node p1,node p2)
 {
     double x1=p1.x-p0.x;
     double y1=p1.y-p0.y;
     double x2=p2.x-p1.x;
     double y2=p2.y-p1.y;
     return x1*x2+y1*y2;
 }
 node miss(node q1,double a,double b,node q2)//求两直线交点坐标
 {
     node ret;
     double c1=a*q1.y-b*q1.x;
     double c2=-a*q2.x-b*q2.y;
     ret.x=-(b*c1+a*c2)/(a*a+b*b);
     ret.y=(a*c1-b*c2)/(a*a+b*b);
     return ret;
 }
 int main()
 {
     int n,i,j;
     while(scanf("%d",&n)!=-)
     {
         node start;
         int tep;
         start.x=start.y=inf;
         for(i=;i<n;i++)
         {
             scanf("%lf%lf",&p[i].x,&p[i].y);
             if(start.y>p[i].y)
             {
                 start=p[i];
                 tep=i;
             }
             else if(fabs(start.y-p[i].y)<eps)
             {
                 if(start.x>p[i].x)
                 {
                     start=p[i];
                     tep=i;
                 }
             }
         }
         p[tep].dis=;
         p[tep].cos=1.0;
         for(i=;i<n;i++)
         {
             if(i!=tep)
             {
                 if(fabs(p[i].x-start.x)<eps&&fabs(p[i].y-start.y)<eps)
                 {
                     p[i].dis=;
                     p[i].cos=1.0;
                 }
                 else
                 {
                     p[i].dis=Len(start,p[i]);
                     p[i].cos=COS(start,p[i]);
                 }
             }
         }
         qsort(p,n,sizeof(p[]),cmp);
         int tt=;
         for(i=;i<n;i++)
         {
             if(fabs(p[i].cos-p[(i+)%n].cos)>eps||fabs(p[i].dis-p[(i+)%n].dis)>eps)
                 pp[tt++]=p[i];
         }
         if(tt==)
         {
             printf("%.5lf\n",0.0);
             for(i=;i<;i++)
                 printf("%.5lf %.5lf\n",p[].x,p[].y);
             continue;
         }
         int flag=;
         for(i=;i<tt-;i++)
         {
             if(fabs(p[i].cos-p[i+].cos)>eps)
                 flag++;
         }
         if(!flag)
         {
             printf("%.5lf\n",0.0);
             printf("%.5lf %.5lf\n",pp[].x,pp[].y);
             printf("%.5lf %.5lf\n",pp[tt-].x,pp[tt-].y);
             printf("%.5lf %.5lf\n",pp[tt-].x,pp[tt-].y);
             printf("%.5lf %.5lf\n",pp[].x,pp[].y);
             continue;
         }
         q[]=pp[tt-];//注意tt；
         q[]=pp[];
         q[]=pp[];
         int cnt=;
         for(i=;i<tt;i++)
         {
             while(cross(q[cnt-],q[cnt],pp[i])<)
             {
                 cnt--;
             }
             q[++cnt]=pp[i];
         }
         int k1,k2;
         k1=;
         j=;
         double S=inf;
         double a[],b[];
         int indx[];
         for(i=;i<cnt;i++)
         {
             double w=sqrt(Len(q[i],q[(i+)%cnt]));
             while(cross(q[i],q[(i+)%cnt],q[(j+)%cnt])>cross(q[i],q[(i+)%cnt],q[j%cnt]))
             {
                 j++;
             }
             double high=cross(q[i],q[(i+)%cnt],q[j%cnt])/w;
             while(dot(q[i],q[(i+)%cnt],q[(k1+)%cnt])>dot(q[i],q[(i+)%cnt],q[(k1)%cnt]))
             {
                 k1++;
             }
             if(i==)
                 k2=k1;
             while(dot(q[i],q[(i+)%cnt],q[(k2+)%cnt])<=dot(q[i],q[(i+)%cnt],q[(k2)%cnt]))
             {
                 k2++;
             }
             double wide=(dot(q[i],q[(i+)%cnt],q[(k1)%cnt])-dot(q[i],q[(i+)%cnt],q[(k2)%cnt]))/w;
             if(S>high*wide)
             {
                 S=high*wide;//更新四个切点坐标以及旋转的直线的方向向量
                 indx[]=i;
                 indx[]=k1%cnt;
                 indx[]=j%cnt;
                 indx[]=k2%cnt;
                 a[]=q[(i+)%cnt].x-q[i].x;
                 b[]=q[(i+)%cnt].y-q[i].y;
                 a[]=b[];
                 b[]=-a[];
                 a[]=a[];
                 b[]=b[];
                 a[]=b[];
                 b[]=-a[];
             }
         }
         printf("%.5lf\n",S);
         node ret[];
         start.x=start.y=inf;

         for(i=;i<;i++)//先找出左下角的点的坐标然后按照极角排序
         {
             ret[i]=miss(q[indx[i]],a[i],b[i],q[indx[(i+)%]]);
             //printf("%.5lf %.5lf\n",ret[i].x,ret[i].y);
             if(start.y>ret[i].y)
             {
                 start=ret[i];
                 tep=i;
             }
             else if(fabs(start.y-ret[i].y)<eps)
             {
                 if(start.x>ret[i].x)
                 {
                      start=ret[i];
                 tep=i;
                 }

             }
         }
         ret[tep].dis=;
         ret[tep].cos=1.5;
         for(i=;i<;i++)
         {
             if(i!=tep)
             {
                 ret[i].dis=Len(start,ret[i]);
                 ret[i].cos=COS(start,ret[i]);
             }
         }
         qsort(ret,,sizeof(ret[]),cmp);
         for(i=;i<;i++)
             printf("%.5lf %.5lf\n",ret[i].x,ret[i].y);
     }
     return ;
 }

整理。