poj1144 关节点

题意也就是找一个网络中的关节点（割点）个数。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
struct node
{
   int i;
   int next;
};
int head[101],pre[101],low[101],ss[101],N,count,cnt;
node edge[10001];
int dfs(int i,int root)
{
    int j,w,k=0;

    if(pre[i]==0) pre[i]=low[i]=++cnt;
    
    for(j=head[i];j;j=edge[j].next)
    { 
		w=edge[j].i;
		if(pre[w]==0)
		{
            dfs(w,i);
			if(low[i]>low[w]) low[i]=low[w];
			if(low[w]>=pre[i]) k++;
		}
		else if(w!=root)
		{
			if(low[i]>pre[w]) low[i]=pre[w];
		}
    }
	if(k) count++;
    return k;
}
int add(int s,int t)
{
    edge[N].i=t;
    edge[N].next=head[s];
    return N++;
}
int main ()
{
   int k,m,n,i,j;
   char c;
   while(scanf("%d",&n) && n)
   {
       N=1;
       memset(head,0,sizeof(head));
	   memset(low,0,sizeof(low));
       while(scanf("%d%c",&m,&c) && m)
       {
           do
           {
			   scanf("%d%c",&k,&c);
               head[m]=add(m,k);
               head[k]=add(k,m);
           }
		   while(c!='\n');
       }
	   memset(pre,0,sizeof(pre));
	   memset(ss,0,sizeof(ss));
       count=cnt=0;
	   for(i=1;i<=n;i++)
	   {
            if(pre[i]==0)
			{
				k=dfs(i,0);
				if(k<2) count--;
			}
	   }
       printf("%d\n",count);
   }
   return 0;
}