poj1144Network (求割点模板题）

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#define maxn 100005
using namespace std;
vector<int> G[maxn];
int dfn[maxn],vis[maxn],low[maxn];     
bool isGedian[maxn];                  //标记该点是否是割点 
int fa[maxn];                         //父亲节点 
int depth;                         
int root;
int ans;
void init(){
    memset(isGedian,0,sizeof(isGedian));
    memset(fa,0,sizeof(fa));
    memset(vis,0,sizeof(vis));
    for(int i = 0;i < maxn;i ++){
        G[i].clear();
    }
}
void dfs(int cur,int depth){
     int cnt = 0;                       //记录当前节点的孩子个数 
     low[cur] = dfn[cur] = depth;
     vis[cur] = true;
     for(int i = 0;i < G[cur].size();i ++){
         int v = G[cur][i];
        if(!vis[v] && v != fa[cur]){
            fa[v] = cur;
            dfs(v,depth+1);
            cnt ++;
            low[cur] = min(low[cur],low[v]);
            if(low[v] >= dfn[cur] && root!= cur){
                if(!isGedian[cur]){
                    ans ++;
                }
                isGedian[cur] = true;
            }
        }
        else{
            low[cur] = min(low[cur],dfn[v]);
        }
     }
     if(root == cur && cnt > 1){
        if(!isGedian[cur]){
            ans ++;
        }
        isGedian[cur] = true;
     }
}
int main()
{
    int n,a,b;
    while(cin >> n && n){
        ans = 0;
        init();
        while(cin >> a && a){
            while(getchar() != ‘\n‘)
            {
                cin >> b;
                G[a].push_back(b);
                G[b].push_back(a);
            }
        }
        root = 1;
        dfs(1,0);
        cout << ans << endl;
    }
    return 0;
}