zju zoj 2588 求割边模板 边双连通

终极模板

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#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;
const int N = 10010;
const int M = 100010;
int min(int a,int b){
    return a>b?b:a;
}
struct EDGE{
    int to,next,id;
}edge[2*M];
int n,m,tot,tdfn,nbridge;
int head[N],vis[N],low[N],dfn[N],bridge[M];
void add(int a,int b,int edgeid){
    //这种方法判重边很慢
    /*    for(j=head[a];j!=-1;j=edge[j].next){
        if(b==edge[j].to)
            break;
    }
    if(j!=-1)
    {
        edge[j].tag=1;
        edge[j^1].tag=1;
        return ;
    }*/
    edge[tot].to=b;
    edge[tot].id=edgeid;
    edge[tot].next=head[a];
    head[a]=tot++;
    edge[tot].to=a;
    edge[tot].id=edgeid;
    edge[tot].next=head[b];
    head[b]=tot++;
}
void dfs(int u,int fa){
    int i,v;low[u]=dfn[u]=++tdfn;vis[u]=1;
    for(i=head[u];i!=-1;i=edge[i].next){
        v=edge[i].to;
        if(vis[v]==1&&edge[i].id!=fa)    low[u]=min(low[u],dfn[v]);
        else if(!vis[v])
        {
            dfs(v,edge[i].id);
            low[u]=min(low[u],low[v]);
            if(low[v]>dfn[u]){
                bridge[edge[i].id]=++nbridge;
            }
        }
    }
    vis[u]=2;
}
void init(){
    int i;
    tdfn=1;tot=0;nbridge=0;
    for(i=0;i<=n;i++) head[i]=-1;
    for(i=1;i<=m;i++) bridge[i]=0;
    for(i=1;i<=n;i++) vis[i]=0;
}
int main()
{
    int i,k,t;
    int u,v;
    scanf("%d",&t);
    while(t--){
        scanf("%d%d",&n,&m);    
        init();
        for(k=1;k<=m;k++)
        {
            scanf("%d%d",&u,&v);
            add(u,v,k);
        }
        dfs(1,0);
        printf("%d\n",nbridge);
        for(i=1,k=nbridge;i<=m;i++)
        {
            if(bridge[i])
            {
                printf("%d",i);
                if(--k) printf(" ");
            }
        }
        if(nbridge) printf("\n");
        if(t) printf("\n");
    }
    return 0;
}