NOIP 模拟 7 回家

#include<bits/stdc++.h>
#define ri register int
#define p(i) ++i
using namespace std;
namespace IO{
    char buf[1<<21],*p1=buf,*p2=buf;
    #define gc() p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++
    inline int read() {
        ri x=0,f=1;char ch=gc();
        while(ch<'0'||ch>'9') {if (ch=='-') f=-1;ch=gc();}
        while(ch>='0'&&ch<='9') {x=(x<<1)+(x<<3)+(ch^48);ch=gc();}
        return x*f; 
    }
}
using IO::read;
namespace nanfeng{
    #define pb(x) push_back(x)
    #define cmax(x,y) ((x)>(y)?(x):(y))
    #define cmin(x,y) ((x)>(y)?(y):(x))
    #define FI FILE *IN
    #define FO FILE *OUT
    static const int N=3.4e5+7;
    int dfn[N],low[N],cut[N],first[N],f[N],st[N],id[N],be[N],bac[N],T,rt,tot,cnt,num,cntd,t=1,n,m,tp;
    struct edge{int v,nxt;}e[N<<2];
    vector<int> dcc[N]; 
    inline void add(int u,int v) {
        e[t].v=v;
        e[t].nxt=first[u];
        first[u]=t++;
    }
    void dfst(int x,int last) {
        dfn[x]=low[x]=p(tot);
        int fg=0;
        st[p(tp)]=x;
        for (ri i(first[x]),v;i;i=e[i].nxt) {
            if (!dfn[v=e[i].v]) {
                dfst(v,x);
                low[x]=cmin(low[x],low[v]);
                if (low[v]>=dfn[x]) {
                    p(fg);
                    if (x!=rt||fg>1) cut[x]=1;
                    p(cnt);
                    int tmp;
                    while((tmp=st[tp--])!=v) dcc[cnt].pb(tmp);
                    dcc[cnt].pb(v);dcc[cnt].pb(x);
                }
            } else if(v!=last) low[x]=cmin(low[x],dfn[v]);
        }
    }
    void dfs(int x,int fa) {
        f[x]=fa;
        for (ri i(first[x]),v;i;i=e[i].nxt) {
            if ((v=e[i].v)==fa) continue;
            dfs(v,x);
        }
    }
    inline void init() {
        memset(first,0,sizeof(first));
        cntd=cnt=tot=tp=0,t=1;
        for (ri i(1);i<=n;p(i)) dcc[i].clear();
        memset(cut,0,sizeof(cut));
        memset(dfn,0,sizeof(dfn));
        memset(low,0,sizeof(low));
        memset(be,0,sizeof(be));
    }
    inline int main() {
        // FI=freopen("nanfeng.in","r",stdin);
        // FO=freopen("nanfeng.out","w",stdout);
        T=read();
        for (ri z(1);z<=T;p(z)) {
            n=read(),m=read();
            init();
            for (ri i(1);i<=m;p(i)) {
                int u=read(),v=read();
                if (u==v) continue;
                add(u,v);add(v,u);
            }
            for (ri i(1);i<=n;p(i)) if (!dfn[i]) rt=i,dfst(i,0);
            t=1;num=cnt;
            memset(first,0,sizeof(first));
            for (ri i(1);i<=n;p(i)) if (cut[i]) id[i]=p(num),bac[num]=i;
            for (ri i(1);i<=cnt;p(i)) {
                for (ri j(0);j<dcc[i].size();p(j)) {
                    int x=dcc[i][j];
                    if (cut[x]) add(id[x],i),add(i,id[x]);
                    else be[x]=i;
                } 
            }
            if (cut[1]) dfs(id[1],0);
            else dfs(be[1],0);
            int x=cut[n]?f[id[n]]:f[be[n]];
            while(f[x]) {
                if (x>cnt) cut[bac[x]]=2,p(cntd);
                x=f[x];
            }
            printf("%d\n",cntd);
            for (ri i(cnt+1);i<=num;p(i)) if (cut[bac[i]]==2) printf("%d ",bac[i]);
            puts(""); 
        }
        return 0;
    }
}
int main() {return nanfeng::main();}