codeforces 277 A Learning Languages 【DFS 】

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 #include<algorithm>
 5 #include<vector>
 6 using namespace std;
 7 
 8 const int maxn = 105;
 9 int g[maxn][maxn],a[maxn][maxn];
10 int vis[maxn];
11 int n,m;
12 
13 void dfs(int u){
14     vis[u] = 1;
15     for(int v = 1;v <= n;v++){
16         if(!vis[v] && g[u][v]) dfs(v);
17     }
18 }
19 
20 int main(){
21     int ans = 0;
22     scanf("%d %d",&n,&m);
23     memset(g,0,sizeof(g));
24     memset(a,0,sizeof(a));
25     int tot = 0;
26     for(int u = 1;u <= n;u++){
27         int k;
28         scanf("%d",&k);
29         if(k == 0) tot++;
30         for(int i = 0;i < k;i++){
31             int v;
32             scanf("%d",&v);
33             a[u][v] = 1;
34         }
35     }
36     
37     if(tot == n) printf("%d\n",tot);
38     else {
39             for(int u = 1;u <= n;u++){
40             for(int v = u+1;v <= n;v++){
41             for(int k = 1;k <= m;k++){
42                 if(a[u][k] && a[v][k]) g[u][v] = g[v][u] = 1;
43             }
44             }
45       }
46     
47     for(int i = 1;i <= n;i++) {
48         if(!vis[i]){
49             ans++;
50             dfs(i);
51         }
52     }
53     printf("%d\n",ans-1);
54     }
55     return 0;
56 }