解题关键：割点模板题。
1 #include<cstdio> 2 #include<cstring> 3 #include<vector> 4 #include<stack> 5 using namespace std; 6 #define N 1010 7 int n,m,ans,pd,son,cut[N],low[N],dfn[N]; 8 stack<int>s; 9 const int maxn=1e5+3; 10 struct Edge{ 11 int nxt; 12 int to; 13 int w; 14 }e[maxn]; 15 int head[maxn],cnt; 16 void add_edge(int u,int v){ 17 e[cnt].to=v; 18 e[cnt].nxt=head[u]; 19 head[u]=cnt++; 20 } 21 void tarjan(int u){ 22 low[u]=dfn[u]=++pd; 23 for(int i=head[u];i!=-1;i=e[i].nxt){ 24 int v=e[i].to; 25 if(!dfn[v]){ 26 tarjan(v); 27 low[u]=min(low[u],low[v]); 28 if(low[v]>=dfn[u]&&u!=1) cut[u]++; 29 else if(u==1) son++; 30 } 31 else low[u]=min(low[u],dfn[v]); 32 } 33 } 34 int main(){ 35 while(scanf("%d",&n)==1&&n){ 36 int u,v; 37 memset(dfn,0,sizeof dfn); 38 memset(cut,0,sizeof cut); 39 memset(head,-1,sizeof head); 40 pd=ans=son=0; 41 while(scanf("%d",&u)==1&&u){ 42 while(getchar()!=' '){ 43 scanf("%d",&v); 44 add_edge(u,v); 45 add_edge(v,u); 46 } 47 } 48 tarjan(1); 49 for(int i=1;i<=n;i++) if(cut[i]) ans++; 50 if(son>1) ans++; 51 printf("%d ",ans); 52 } 53 return 0; 54 }