uva_ 796 - Critical Links

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
#include<cmath>
#include<utility>
#include<set>
#include<vector>
#include<cstring>
using namespace std;

vector<int>to[10010];
int dfsn[10010],low[10010],tim,n;
vector<pair<int,int> >ans;
void reset(){
        for(int i=0;i<n;i++) to[i].clear();
        tim=0;
        ans.clear();
        memset(dfsn,-1,sizeof(dfsn)) ;
        memset(low,0,sizeof(low)) ;

}


void DFS(int u,int p)
{

    dfsn[u]=low[u]=++tim;

    for(int i=0;i<(int)to[u].size();i++)
    {
        int v=to[u][i];
        if(dfsn[v]==-1){
            DFS(v,u);
            low[u]=min(low[u],low[v]);
            if(low[v]>dfsn[u]){
                if(u>v) ans.push_back(make_pair(v,u));
                else ans.push_back(make_pair(u,v));
            }
        }

        else if(v!=p)low[u]=min(low[u],dfsn[v]);

    }

}


int main(){

     freopen("C:\\Users\\Mazhar\\Desktop\\Text_Files\\in.txt", "r", stdin);

     //bool blank = true ;

     while(scanf("%d",&n)!=EOF){


       // if(blank) blank = false ;
       // else printf("\n") ;

        reset() ;
        for(int i=0;i<n;i++){
            int u,k;
            scanf("%d (%d)",&u,&k);

            while(k--){
                int v;
                scanf("%d",&v);
                to[u].push_back(v);
              //  to[v].push_back(u);
            }

        }



        for(int i=0;i<n;i++){
            if(dfsn[i]==-1)   DFS(i,-1);
        }



       sort(ans.begin(),ans.end());

       printf("%d critical links\n",int(ans.size()));

       for(int i=0;i<(int)ans.size();i++)
       {

            printf("%d - %d\n",ans[i].first,ans[i].second);
       }

       printf("\n");


     }




    return 0;
}