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;

}