HHHOJ 2018.10.4 ACM 造桥

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 double path[105][105];
 4 bool f=0;
 5 int n,m,tot=0,p,ansa,ansb;
 6 double x[105],y[105];
 7 int q[105],top=0;
 8 double anss=2e9;
 9 double getlen(int a,int b){return (double)sqrt((x[a]-x[b])*(x[a]-x[b])+(y[a]-y[b])*(y[a]-y[b]));}
10 int main() 
11 {
12     freopen("bridge.in","r",stdin);
13     freopen("bridge.out","w",stdout);
14     cin>>n;    
15     x[0]=0;y[0]=0;
16     for (int i=1;i<=n;i++) cin>>x[i]>>y[i];
17     cin>>m;    
18     for (int i=0;i<=n;i++)for (int j=0;j<=n;j++)path[i][j]=2e9;
19     for (int i=1;i<=m;i++)
20     {
21         int a,b;
22         cin>>a>>b;
23         path[a][b]=path[b][a]=getlen(a,b);
24     }
25     cin>>p;
26     for (int k=0;k<=n;k++)
27      for (int i=0;i<=n;i++)
28       for (int j=0;j<=n;j++)
29         path[i][j]=min(path[i][j],path[i][k]+path[k][j]);
30     for (int i=0;i<=n;i++) path[i][i]=0;
31     for(int i=1;i<=n;i++)if(path[i][0]>p)q[++top]=i;
32     for (int i=0;i<=n;i++) 
33      for (int j=i+1;j<=n;j++)
34      {
35       bool flag=0;
36       double ans=getlen(i,j);
37       if(path[i][j]==ans||ans>anss)continue;
38       for (int k=1;k<=top;k++) if (path[q[k]][i]+ans+path[j][0]>p&&path[q[k]][j]+ans+path[i][0]>p) {flag=1;break;}
39       if (flag==0) if (anss==ans) tot++;else anss=ans,tot=1,ansa=i,ansb=j; 
40     }
41     if(tot==0) {cout<<0<<endl;return 0;}
42     if (tot==1) cout<<ansa<<" "<<ansb<<endl;else cout<<tot<<endl;
43     return 0;
44 }
45 /*
46 5
47 1 3
48 2 -3
49 6 -2
50 3 2
51 5 1
52 5
53 0 1
54 2 1
55 4 0
56 2 3
57 5 4
58 10
59 */