POJ 1523 （Tarjan求关节点）

http://poj.org/problem?id=1523

#define IO std::ios::sync_with_stdio(0)
#include <iostream>
#include <vector>
#include <stdio.h>
#include <string.h>
#define pb push_back
using namespace std;
typedef long long ll;

const int N=1005;

vector<int>g[N];

int n,cnt;
int vis[N],low[N],ans[N];

void dfs(int u){
    low[u]=vis[u]=++cnt;
    for(int i=0;i<g[u].size();i++){
        int v=g[u][i];
        if(!vis[v]){
            dfs(v);
            if(low[v]>=vis[u])ans[u]++;
            low[u]=min(low[u],low[v]);
        }
        else low[u]=min(low[u],vis[v]);
    }
}

void init(){
    cnt=0;
    vis[1]=1;
    memset(vis,0,sizeof(vis));
    memset(low,0,sizeof(low));
    memset(ans,0,sizeof(ans));
}


int main(){
    int a,b;
    int Case=1;
    while(1)
    {
        while(scanf("%d",&a)&&a)
        {
 
            scanf("%d",&b);
            g[a].push_back(b);
            g[b].push_back(a);
        }
        init();

        dfs(1);
        if(Case>1)
            cout<<endl;
        printf("Network #%d\n",Case++);
        int flag=1;
        ans[1]--;
        for(int i=1; i<=1000; i++)
            if(ans[i]>0)
            {
                flag=0;
                printf("  SPF node %d leaves %d subnets\n",i,ans[i]+1);
            }
        if(flag)
            cout<<"  No SPF nodes"<<endl;
 
 
        for(int i=1; i<=1000; i++)
            g[i].clear();
        scanf("%d",&a);
        if(a==0)
            break;
        scanf("%d",&b);
        g[a].push_back(b);
        g[b].push_back(a);
    }
    return 0;

}