图论——连通图

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<string>
 4 #include<cstring>
 5 #include<algorithm>
 6 #include<vector>
 7 using namespace std;
 8 const int maxn = 105;
 9 const int maxint = 100000000;
10 int n,m,g[maxn][maxn],tg[maxn][maxn],ans,nowans;
11 void input(){
12     cin>>n>>m;
13     int u,v;
14     for(int i = 1;i <= m;i++){
15         cin>>u>>v;
16         g[u][v] = 1;
17     }
18 }
19 void build(){
20     for(int k = 1;k <= n;k++){
21         for(int i = 1;i <= n;i++){
22             for(int j = 1;j <= n;j++){
23                 if(k != i && k != j && i != j) g[i][j] = g[i][j] || (g[i][k] && g[k][j]);
24             }
25         }
26     }
27     for(int i = 1;i <= n;i++){
28         nowans = 0;
29         for(int j = 1;j <= n;j++){
30             if(g[i][j]) nowans++;
31             if(g[j][i]) nowans++;
32         }
33         if(nowans == n-1) ans++;
34     }
35     cout<<ans<<endl;
36 }
37 int main(){
38     input();
39     build();
40 }