1 /**
2 旋转卡壳，，
3 **/
4 #include <iostream>
5 #include <algorithm>
6 #include <cmath>
7 #include <cstdio>
8 using namespace std;
9
10 const double eps = 1e-8;
11 struct point {
12 double x,y;
13 point(double x=0,double y =0):x(x),y(y){}
14 };
15
16 int dcmp(double x){
17 if(fabs(x)<eps)
18 return 0;
19 else
20 return x<0?-1:1;
21 }
22
23 point p[10020],p1[10020];
24 point q[10020],q1[10020];
25 int maxid,minid;
26 int N,M;
27 typedef point Vector;
28
29 Vector operator -(point a,point b){
30 return Vector(a.x-b.x,a.y-b.y);
31 }
32
33 double cross(Vector a,Vector b){
34 return a.x*b.y-a.y*b.x;
35 }
36
37 double dot(Vector a,Vector b){
38 return a.x*b.x+a.y*b.y;
39 }
40 bool cmp(point a,point b){
41 if(a.x==b.x)
42 return a.y<b.y;
43 return a.x<b.x;
44 }
45
46 bool operator ==(const point &a,const point &b){
47 return dcmp(a.x-b.x)==0&&dcmp(a.y-b.y)==0;
48 }
49
50 double length(Vector a){
51 return sqrt(a.x*a.x+a.y*a.y);
52 }
53
54 int convexHull(point *p,int n,point *ch){
55 sort(p,p+n,cmp);
56 int m =0;
57 for(int i=0;i<n;i++){
58 while(m>1&&cross(ch[m-1]-ch[m-2],p[i]-ch[m-2])<=0)
59 m--;
60 ch[m++] = p[i];
61 }
62 int k =m;
63 for(int i = n-2;i>=0;i--){
64 while(m>k&&cross(ch[m-1]-ch[m-2],p[i]-ch[m-2])<=0)
65 m--;
66 ch[m++] = p[i];
67 }
68 if(n>1) m--;
69 return m;
70 }
71
72 double distanceToSegment(point p,point a,point b){
73 if(a==b)
74 return length(p-a);
75 Vector v1 = b-a,v2 = p-a, v3 = p-b;
76 if(dcmp(dot(v1,v2))<0)
77 return length(v2);
78 else if(dcmp(dot(v1,v3))>0)
79 return length(v3);
80 else
81 return fabs(cross(v1,v2))/length(v1);
82 }
83
84 double distanceBetweenSegment(point a,point b,point c,point d){
85 return min(min(distanceToSegment(a,c,d),distanceToSegment(b,c,d)),min(distanceToSegment(c,a,b),distanceToSegment(d,a,b)));
86 }
87
88 void getMaxAndMin(int &maxid,int &minid){
89 maxid =0;
90 minid =0;
91 for(int i=1;i<N;i++){
92 if(p1[i].y<p1[minid].y)
93 minid =i;
94 }
95 for(int i=0;i<M;i++){
96 if(q1[i].y>q1[maxid].y)
97 maxid = i;
98 }
99 }
100
101 double solve(point *p,point *q,int minid,int maxid,int N,int M){
102 double temp,ret = 1e5;
103 p[N] = p[0];
104 q[M] = q[0];
105 for(int i=0;i<N;i++){
106 while(temp = dcmp(cross(q[maxid]-q[maxid+1],p[minid+1]-p[minid]))>0){
107 maxid = (maxid+1)%M;
108 }
109 if(temp<0)
110 ret = min(ret,distanceToSegment(q[maxid],p[minid],p[minid+1]));
111 else
112 ret = min(ret,distanceBetweenSegment(p[minid],p[minid+1],q[maxid],q[maxid+1]));
113 minid = (minid+1)%N;
114 }
115 return ret;
116 }
117
118 int main()
119 {
120
121 while(cin>>N>>M){
122 if(N==0&&M==0)
123 break;
124 for(int i=0;i<N;i++)
125 cin>>p[i].x>>p[i].y;
126 for(int i=0;i<M;i++)
127 cin>>q[i].x>>q[i].y;
128 N = convexHull(p,N,p1);
129 M = convexHull(q,M,q1);
130 getMaxAndMin(maxid,minid);
131 double ans = solve(p1,q1,minid,maxid,N,M);
132 printf("%.5lf\n",ans);
133 }
134 return 0;
135 }
poj 3608 Bridge Across Islands 两凸包间最近距离
时间： 2024-10-13 00:17:55