[poj1144]Network（求割点模板）

解题关键：割点模板题。

 #include<cstdio>
 #include<cstring>
 #include<vector>
 #include<stack>
 using namespace std;
 #define N 1010
 int n,m,ans,pd,son,cut[N],low[N],dfn[N];
 stack<int>s;
 const int maxn=1e5+;
 struct Edge{
     int nxt;
     int to;
     int w;
 }e[maxn];
 int head[maxn],cnt;
 void add_edge(int u,int v){
     e[cnt].to=v;
     e[cnt].nxt=head[u];
     head[u]=cnt++;
 }
 void tarjan(int u){
     low[u]=dfn[u]=++pd;
     for(int i=head[u];i!=-;i=e[i].nxt){
         int v=e[i].to;
         if(!dfn[v]){
             tarjan(v);
             low[u]=min(low[u],low[v]);
             if(low[v]>=dfn[u]&&u!=) cut[u]++;
             else if(u==) son++;
         }
         else low[u]=min(low[u],dfn[v]);
     }
 }
 int main(){
     while(scanf("%d",&n)==&&n){
         int u,v;
         memset(dfn,,sizeof dfn);
         memset(cut,,sizeof cut);
         memset(head,-,sizeof head);
         pd=ans=son=;
         while(scanf("%d",&u)==&&u){
             while(getchar()!='\n'){
                 scanf("%d",&v);
                 add_edge(u,v);
                 add_edge(v,u);
             }
         }
         tarjan();
         for(int i=;i<=n;i++) if(cut[i]) ans++;
         if(son>) ans++;
         printf("%d\n",ans);
     }
     return ;
 }