[Kuangbin take you to fly] thematic nine connected graph C - Critical Links UVA - 796

This question is to ask the number of bridges.

Then there are the corresponding theorem of bridge judgment:

And u in adjacent nodes, there is a node is the smallest timestamp than the
current u access to a large order, that this point can only be reached by u fruit, then the
adjacent edges between them is the bridge

#include<iostream>
#include<string.h>
#include<algorithm>
#include<stdio.h>
using namespace std;
const int SIZE = 100010;
struct node{
  int u,v;
}brige[SIZE];
int head[SIZE],ver[SIZE*2],Next[SIZE*2];
int dfn[SIZE],low[SIZE],n,m,tot,num,cnt;
void add(int x,int y){
   ver[++tot]=y,Next[tot]=head[x],head[x]=tot;
}
voidTarjan ( int U, int pre) { 
  DFN [U] = Low [U] ++ = NUM;
   for ( int I = head [U]; I; I = the Next [I]) {
     int V = Ver [I] ;
     IF (V == pre) Continue ;
     IF (! DFN [V]) { 
        Tarjan (V, U); 
        Low [U] = min (Low [U], Low [V]);
         IF (Low [V] > DFN [u]) {
             / * 
            in adjacent nodes and u, there is one node is the smallest timestamp than 
            the current u order to access large, that is to say the point u can be reached by the fruit, then 
            between their adjacent side is the bridge 
            * / 
            cnt ++; 
            care [cnt] .u = u; 
            care [cnt] .v = v;
            if (care [cnt] .u> care [cnt] .v) { 
                swap (care [cnt] .u, care [cnt] .v); 
            } 
        } 
    } 
    Else  if (low [u]> dfn [v]) 
        medium [u] = min (low [in], DFN [v]); 
  } 
} 
Void init () { 
   MEMS (care, 0 , sizeof (care)); 
   MEMS (low, 0 , sizeof (low)); 
   MEMS (ver, 0 , sizeof(ver));
   memset(dfn,0,sizeof(dfn));
   memset(Next,0,sizeof(Next));
   memset(head,0,sizeof(head));
   cnt=0;
   num=0;
   tot=1;
}
bool cmp(node a,node b){
   if (a.u==b.u)return a.v<b.v;
   return a.u<b.u;
}
int main(){
  int id,tmp,nx;
  while(~scanf("%d",&n)){
    if (n==0){
        printf("0 critical links\n\n");
        continue;
    }
    init();
    for(int i=1;i<=n;i++){
        scanf("%d",&id);
        id++;
        getchar();
        getchar();
        scanf("%d",&tmp);
        getchar();
        for (int j=1;j<=tmp;j++){
            scanf("%d",&nx);
            nx++;
            add(id,nx);
            add(nx,id);
        }
    }
    for (int i=1;i<=n;i++){
        if(!dfn[i])tarjan(i,i);
    }
    printf("%d  critical links\n",cnt);
    sort(brige+1,brige+1+cnt,cmp);
    for (int i=1;i<=cnt;i++){
        printf("%d - %d\n",brige[i].u-1,brige[i].v-1);
    }
   printf("\n");

  }
  return 0;
}
/*
3 critical links
0 - 1
3 - 4
6 - 7

*/