Codeforces Round #360 C

#include "iostream"
#include "string.h"
#include "stack"
#include "queue"
#include "string"
#include "vector"
#include "set"
#include "map"
#include "algorithm"
#include "stdio.h"
#include "math.h"
#pragma comment(linker, "/STACK:102400000,102400000")
#define ll long long
#define bug(x) cout<<x<<" "<<"UUUUU"<<endl;
#define mem(a,x) memset(a,x,sizeof(a))
#define mp(x,y) make_pair(x,y)
#define pb(x) push_back(x)
#define lrt (rt<<1)
#define rrt (rt<<1|1)
using namespace std;
const long long INF = 1e18+1LL;
const int inf = 1e9+1e8;
const int N=1e5+100;
const ll mod=1e9+7;

///CCCC
int cl[N<<1],vis[N<<1],nex[N<<2],head[N<<1],to[N<<1],id[N<<1],tot,flag,ans[3];
void add(int u, int v){
    to[tot]=v;
    nex[tot]=head[u];
    head[u]=tot++;
}
void dfs(int u,int c){ //bug("xx")
    if(cl[u]==c){
        flag=1;
        return;
    }
    cl[u]=c^1;
    ans[c^1]++;
    for(int i=head[u]; i!=-1; i=nex[i]){
        int v=to[i];
        if(cl[v]!=-1){
            if(cl[u]==cl[v]){
                flag=1;
                return;
            }
            continue;
        }
        dfs(v,cl[u]);
    }
}
int main(){
    int n,m,u,v;
    cin>>n>>m;
    mem(head,-1), mem(cl,-1);
    for(int i=1; i<=m; ++i){
        cin>>u>>v;
        add(u,v);
        add(v,u);
        id[u]=1;
        id[v]=1;
    }
    for(int i=1; i<=n; ++i){ //cout<<cl[i]<<" "<<id[i]<<"\n";
        if(cl[i]==-1 && id[i]==1) dfs(i,1);
        if(flag){
            cout<<"-1\n";
            return 0;
        }
    }
    cout<<ans[0]<<"\n";
    for(int i=1; i<=n; ++i){
        if(id[u] && cl[i]==0){
            cout<<i<<" ";
        }
    }
    cout<<"\n";
    cout<<ans[1]<<"\n";
    for(int i=1; i<=n; ++i){
        if(id[u] && cl[i]==1){
            cout<<i<<" ";
        }
    }
    return 0;
}