poj 3608 Bridge Across Islands 两凸包间最近距离

 /**
 旋转卡壳，，
 **/
 #include <iostream>
 #include <algorithm>
 #include <cmath>
 #include <cstdio>
 using namespace std;

 const double eps = 1e-;
 struct point {
     double x,y;
     point(double x=,double y =):x(x),y(y){}
 };

 int dcmp(double x){
     if(fabs(x)<eps)
         return ;
     else
         return x<?-:;
 }

 point p[],p1[];
 point q[],q1[];
 int maxid,minid;
 int N,M;
 typedef point Vector;

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

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

 double dot(Vector a,Vector b){
     return a.x*b.x+a.y*b.y;
 }
 bool  cmp(point a,point b){
     if(a.x==b.x)
         return a.y<b.y;
     return a.x<b.x;
 }

 bool operator ==(const point &a,const point &b){
     return dcmp(a.x-b.x)==&&dcmp(a.y-b.y)==;
 }

 double length(Vector a){
     return sqrt(a.x*a.x+a.y*a.y);
 }

 int convexHull(point *p,int n,point *ch){
     sort(p,p+n,cmp);
     int m =;
     for(int i=;i<n;i++){
         while(m>&&cross(ch[m-]-ch[m-],p[i]-ch[m-])<=)
             m--;
         ch[m++] = p[i];
     }
     int k =m;
     for(int i = n-;i>=;i--){
         while(m>k&&cross(ch[m-]-ch[m-],p[i]-ch[m-])<=)
             m--;
         ch[m++] = p[i];
     }
     if(n>) m--;
     return m;
 }

 double distanceToSegment(point p,point a,point b){
     if(a==b)
         return length(p-a);
     Vector v1 = b-a,v2 = p-a, v3 = p-b;
     if(dcmp(dot(v1,v2))<)
         return length(v2);
     else if(dcmp(dot(v1,v3))>)
         return length(v3);
     else
         return fabs(cross(v1,v2))/length(v1);
 }

 double distanceBetweenSegment(point a,point b,point c,point d){
     return min(min(distanceToSegment(a,c,d),distanceToSegment(b,c,d)),min(distanceToSegment(c,a,b),distanceToSegment(d,a,b)));
 }

 void getMaxAndMin(int &maxid,int &minid){
     maxid =;
     minid =;
     for(int i=;i<N;i++){
         if(p1[i].y<p1[minid].y)
             minid =i;
     }
     for(int i=;i<M;i++){
         if(q1[i].y>q1[maxid].y)
             maxid = i;
     }
 }

 double solve(point *p,point *q,int minid,int maxid,int N,int M){
     double temp,ret = 1e5;
     p[N] = p[];
     q[M] = q[];
     for(int i=;i<N;i++){
         while(temp = dcmp(cross(q[maxid]-q[maxid+],p[minid+]-p[minid]))>){
             maxid = (maxid+)%M;
         }
         if(temp<)
             ret = min(ret,distanceToSegment(q[maxid],p[minid],p[minid+]));
         else
             ret = min(ret,distanceBetweenSegment(p[minid],p[minid+],q[maxid],q[maxid+]));
         minid = (minid+)%N;
     }
     return ret;
 }

 int main()
 {

     while(cin>>N>>M){
         if(N==&&M==)
             break;
         for(int i=;i<N;i++)
             cin>>p[i].x>>p[i].y;
         for(int i=;i<M;i++)
             cin>>q[i].x>>q[i].y;
         N = convexHull(p,N,p1);
         M = convexHull(q,M,q1);
         getMaxAndMin(maxid,minid);
         double ans = solve(p1,q1,minid,maxid,N,M);
         printf("%.5lf\n",ans);
     }
     return ;
 }