poj1144 求割点的个数

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <stack>
using namespace std;
const int M = 1009;
int n,m;
int dfn[M],low[M];
int dfs_clock;
bool iscut[M];
vector<int> G[M];
void init()
{
dfs_clock = 0;
for(int i = 0;i <= 2*n;i++) G[i].clear();
memset(dfn,0,sizeof(dfn));
memset(iscut,false,sizeof(iscut));
}
int dfs(int u,int fa)
{
int lowu = dfn[u] = ++dfs_clock;
int child = 0;
for(int i = 0;i < G[u].size();i++)
{
int v = G[u][i];
if(!dfn[v])
{
child++;
int lowv = dfs(v,u);
lowu = min(lowu,lowv);
if(lowv >= dfn[u]) iscut[u] = true;
}
else if(dfn[v] < dfn[u] && v != fa)
{
lowu = min(lowu,dfn[v]);
}
}
if(fa < 0 && child == 1) iscut[u] = false;
low[u] = lowu;
return lowu;
}
int main()
{
while(scanf("%d",&n) == 1 && n)
{
int a;
init();
while(scanf("%d",&a) == 1 && a)
{
while(getchar() != '\n')
{
int b;
scanf("%d",&b);
G[a].push_back(b);
G[b].push_back(a);
}
}
dfs(1,-1);
int ans = 0;
for(int i = 1;i <= n;i++)
{
if(iscut[i]) ans++;
}
printf("%d\n",ans);
}
return 0;
}