luoguP1354房间最短路问题

判断两点间连通性，建图跑floyed

 #include<bits/stdc++.h>
 using namespace std;
 const int N=;
 struct node
 {
     double z[],x;
 }q[N];double e[N][N];
 double dis(double x1,double y1,double x2,double y2)
 {
     return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
 }
 bool come(int i,int j,int a,int b)
 {
     if(j-i<)return ;
     double x1=q[i].x,x2=q[j].x,y1=q[i].z[a],y2=q[j].z[b];if(x1==x2)return ;
     double k=(y1-y2)/(x1-x2),bb=y1-x1*k;
     for(i=i+;i<j;++i)
     {
         double y=q[i].x*k+bb;
         if(y<q[i].z[]||(y>q[i].z[]&&y<q[i].z[])||y>q[i].z[])return ;
     }
     return ;
 }
 void add(int i,int j,int a,int b)
 {
     if(come(i,j,a,b))return;
     e[i*+a][j*+b]=e[j*+b][i*+a]=dis(q[i].x,q[i].z[a],q[j].x,q[j].z[b]);
 }
 int main()
 {
     int n;
     scanf("%d",&n);
     for(int i=;i<=n;++i)
     {
         scanf("%lf",&q[i].x);
         for(int j=;j<=;++j)scanf("%lf",&q[i].z[j]);
     }
     q[].x=;q[++n].x=;
     for(int i=;i<=;++i)q[].z[i]=q[n].z[i]=;
     for(int i=;i<=n*+;++i)for(int j=;j<=n*+;++j)e[i][j]=1e9;

     for(int i=;i<=n;++i)
     for(int j=i+;j<=n;++j)
     for(int a=;a<=;++a)
     for(int b=;b<=;++b)
     add(i,j,a,b);
     for(int k=;k<=n*+;++k)
     for(int i=;i<=n*+;++i)
     for(int j=;j<=n*+;++j)
     e[i][j]=min(e[i][j],e[i][k]+e[k][j]);
     printf("%.2lf",e[][n*+]);
     return ;
 }