luoguP1354房间最短路问题

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int N=105;
 4 struct node
 5 {
 6     double z[5],x;
 7 }q[N];double e[N][N];
 8 double dis(double x1,double y1,double x2,double y2)
 9 {
10     return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
11 }
12 bool come(int i,int j,int a,int b)
13 {
14     if(j-i<2)return 0;
15     double x1=q[i].x,x2=q[j].x,y1=q[i].z[a],y2=q[j].z[b];if(x1==x2)return 1;
16     double k=(y1-y2)/(x1-x2),bb=y1-x1*k;
17     for(i=i+1;i<j;++i)
18     {
19         double y=q[i].x*k+bb;
20         if(y<q[i].z[1]||(y>q[i].z[2]&&y<q[i].z[3])||y>q[i].z[4])return 1;
21     }
22     return 0;
23 }
24 void add(int i,int j,int a,int b)
25 {
26     if(come(i,j,a,b))return;
27     e[i*4+a][j*4+b]=e[j*4+b][i*4+a]=dis(q[i].x,q[i].z[a],q[j].x,q[j].z[b]);
28 }
29 int main()
30 {
31     int n;
32     scanf("%d",&n);
33     for(int i=1;i<=n;++i)
34     {
35         scanf("%lf",&q[i].x);
36         for(int j=1;j<=4;++j)scanf("%lf",&q[i].z[j]);
37     }
38     q[0].x=0;q[++n].x=10;
39     for(int i=1;i<=4;++i)q[0].z[i]=q[n].z[i]=5;
40     for(int i=1;i<=n*4+4;++i)for(int j=1;j<=n*4+4;++j)e[i][j]=1e9;
41     
42     for(int i=0;i<=n;++i)
43     for(int j=i+1;j<=n;++j)
44     for(int a=1;a<=4;++a)
45     for(int b=1;b<=4;++b)
46     add(i,j,a,b);
47     for(int k=1;k<=n*4+4;++k)
48     for(int i=1;i<=n*4+4;++i)
49     for(int j=1;j<=n*4+4;++j)
50     e[i][j]=min(e[i][j],e[i][k]+e[k][j]);
51     printf("%.2lf",e[1][n*4+1]);
52     return 0;
53 }