hdu 4034 Graph

 1

http://acm.hdu.edu.cn/showproblem.php?pid=4034

 vis[][]作用是 防止一条边被删多次
 2 
 3 #include<stdio.h>
 4 #include<string.h>
 5 #define N 1000
 6 int ans;
 7 int map[N][N],n,f,vis[N][N];
 8 void search()
 9 {
10     int i,j,k;
11     memset(vis,0,sizeof(vis));
12     for(k=1;k<=n;k++)
13     {
14         for(i=1;i<=n;i++)
15         {
16             if(i==k)continue;
17             for(j=1;j<=n;j++)
18             {
19                 if(i==j||j==k)continue;
20                 if(map[i][j]==map[i][k]+map[k][j]&&!vis[i][j])
21              {
22                  //printf("%d %d %d \n",i,k,j);
23                     ans--;
24                     vis[i][j]=1;
25 
26                }
27                if(map[i][j]>map[i][k]+map[k][j])
28                 {
29                       f=1;
30                       return ;
31 
32                 }
33 
34 
35             }
36         }
37     }
38 }
39 int main()
40 {
41     int T;
42     int l,i,j;
43     scanf("%d",&T);
44     for(l=1;l<=T;l++)
45     {
46         scanf("%d",&n);
47         for(i=1;i<=n;i++)
48           for(j=1;j<=n;j++)
49            scanf("%d",&map[i][j]);
50             ans=(n-1)*n;
51              printf("Case %d: ",l);
52              f=0;
53            search();
54 
55            if(!f)
56            printf("%d\n",ans);
57            else printf("impossible\n");
58 
59     }
60 
61 }