UVa 208 Firetruck【回溯】

 1 #include<iostream>  
 2 #include<cstdio>  
 3 #include<cstring> 
 4 #include <cmath> 
 5 #include<stack>
 6 #include<vector>
 7 #include<map> 
 8 #include<set>
 9 #include<queue> 
10 #include<algorithm>  
11 using namespace std;
12 
13 #define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)
14 
15 typedef long long LL;
16 const int INF = (1<<30)-1;
17 const int mod=1000000007;
18 const int maxn=55;
19 
20 int d[maxn][maxn],rute[maxn],vis[maxn];
21 int en,n,ans;
22 
23 void dfs(int x,int cnt){
24     if(x==en){
25         printf("1");
26         for(int i=1;i<cnt-1;i++) printf(" %d",rute[i]);
27         printf(" %d\n",en);
28         ans++;
29         return;        
30     }
31     
32     for(int i=2;i<=n;i++){
33         if(!vis[i]&&d[x][i]==1&&d[i][en]!=INF){            

34             rute[cnt]=i;
35             vis[i]=1;
36             dfs(i,cnt+1);
37             vis[i]=0;
38         }
39     }
40 }
41  
42 
43 int main(){
44     int kase=0;
45     while(scanf("%d",&en)!=EOF){
46         int u,v;
47         n=-1;
48         for(int i=1;i<=55;i++){
49             for(int j=1;j<=55;j++) {
50                 d[i][j]=INF;
51             }        
52         }
53              
54         while(scanf("%d %d",&u,&v)&&(u||v)){
55             d[u][v]=d[v][u]=1;
56             n=max(max(u,v),n);//找出这张图里面最大的点的标号                    
57         }
58         
59         for(int k=1;k<=n;k++)
60          for(int i=1;i<=n;i++)
61           for(int j=1;j<=n;j++)
62           d[i][j]=min(d[i][j],d[i][k]+d[k][j]);
63           
64           ans=0;
65           memset(vis,0,sizeof(vis));
66           
67           printf("CASE %d:\n", ++kase);    
68           dfs(1,1);    
69           printf("There are %d routes from the firestation to streetcorner %d.\n", ans, en);
70     }
71     return 0;    
72 }