COGS8. 备用交换机

#include<iostream>
#include<cstdio>
#include<cstring>
#define maxn 1200
using namespace std;
 
int n,x,y,sumedge,ans,root,tim;
int low[maxn],dfn[maxn],head[maxn],iscut[maxn];
 
struct Edge{
    int x,y,nxt;
    Edge(int x=0,int y=0,int nxt=0):
        x(x),y(y),nxt(nxt){}
}edge[maxn<<1];
 
void add(int x,int y){
    edge[++sumedge]=Edge(x,y,head[x]);
    head[x]=sumedge;
}
 
void Tarjian(int x,int fa){
    int cnt=0;low[x]=dfn[x]=++tim;
    for(int i=head[x];i;i=edge[i].nxt){
        int v=edge[i].y;
        if(v==fa)continue;
        if(dfn[v]==0){
            cnt++;Tarjian(v,x);
            low[x]=min(low[x],low[v]);
            if(low[v]>=dfn[x]&&x!=root&&iscut[x]==0)iscut[x]=1,ans++;
            if(x==root&&cnt>=2&&iscut[x]==0)iscut[x]=1,ans++;
        }else low[x]=min(low[x],dfn[v]);
    }
}
 
int main(){
    freopen("gd.in","r",stdin);
    freopen("gd.out","w",stdout);
    scanf("%d",&n);
    while(scanf("%d%d",&x,&y)!=EOF){
        add(x,y);add(y,x);
    }
    for(int i=1;i<=n;i++)
     if(!dfn[i])root=i,Tarjian(i,i);
    printf("%d\n",ans);
    for(int i=1;i<=n;i++)
     if(iscut[i]) printf("%d\n",i);
    fclose(stdin);fclose(stdout);
    return 0;
}