poj1556The Doors

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枚举两点 若不和任何线段相交 建边为dis（i,j) floyd求最短路

 #include <iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<stdlib.h>
 #include<vector>
 #include<cmath>
 #include<queue>
 #include<set>
 using namespace std;
 #define N 100
 #define LL long long
 #define INF 0xfffffff
 const double eps = 1e-;
 const double pi = acos(-1.0);
 const double inf = ~0u>>;
 struct point
 {
     double x,y;
     point(double x=,double y=):x(x),y(y){}
 }p[N];
 struct line
 {
     point u,v;
 }li[N];
 double w[N][N];
 typedef point pointt;
 pointt operator - (point a,point b)
 {
     return pointt(a.x-b.x,a.y-b.y);
 }
 int dcmp(double x)
 {
     if(fabs(x)<eps) return ;
     return x<?-:;
 }
 double dis(point a)
 {
     return sqrt(a.x*a.x+a.y*a.y);
 }
 double cross(point a,point b)
 {
     return a.x*b.y-a.y*b.x;
 }
 bool segprointer(point a1,point a2,point b1,point b2)
 {
     double c1 = cross(a2-a1,b1-a1),c2 = cross(a2-a1,b2-a1),
     c3  = cross(b2-b1,a1-b1),c4 = cross(b2-b1,a2-b1);
     return dcmp(c1)*dcmp(c2)<&&dcmp(c3)*dcmp(c4)<;
 }
 int main()
 {
     int n,i,j,k;
     while(scanf("%d",&n)!=EOF)
     {
         if(n==-) break;
         int g = ;
         for(i = ; i <=  ; i++)
         {
             for(j = ;  j<=  ; j++)
             w[i][j] = INF;
             w[i][i] = ;
         }
         int o = ;
         for(i = ; i <= n ;i++)
         {
             double k;
             scanf("%lf",&k);
             for(j = ; j <= ; j++)
             {
                 p[++g].x = k;
                 scanf("%lf",&p[g].y);
             }
             point pp = point(k,);
             li[++o].u = pp;
             li[o].v = p[g-];
             li[++o].u = p[g-];
             li[o].v = p[g-];
             li[++o].u = p[g];
             pp = point(k,);
             li[o].v = pp;
         }
         p[g+] = point(,);
         p[g+] = point(,);
         //printf("%d\n",segprointer(p[g+1],p[g+2],li[5].u,li[5].v));
         for(i = ; i <= g+; i++)
             for(j = i+; j <= g+; j++)
             {
                 if(i==j) continue;
                 for(k = ; k <= o ; k++)
                 {
                     if(segprointer(p[i],p[j],li[k].u,li[k].v))break;
 
                 }
                 if(k>o)
                 w[i][j] = w[j][i] = dis(p[i]-p[j]);
                 //printf("%.2f %.2f %.2f %.2f %.2f\n",p[i].x,p[i].y,p[j].x,p[j].y,w[i][j]);
             }
         for(i = ; i <= g+ ; i++)
             for(j = ; j <=g+ ;j++)
                 for(k = ; k <= g+ ; k++)
                 w[j][k] = min(w[j][i]+w[i][k],w[j][k]);
         printf("%.2f\n",w[g+][g+]);
     }
     return ;
 }