code:

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+20;
int a[2*N],b[2*N];
void solve(){
    int n;
    scanf("%d",&n);
    for(int i=1;i<=2*n;i++)scanf("%d",a+i);
    for(int i=1;i<=2*n;i++)scanf("%d",b+i);
    printf("%d\n",2*n);
    for(int i=1;i<=2*n;i++){
        if(i<=n){
            if(b[i]==1)a[i]=3;
            if(b[i]==2)a[i]=1;
            if(b[i]==3)a[i]=2;
        }
        printf("%d ",a[i]);
    }
    puts("");
    for(int i=1;i<=2*n;i++){
        if(i>n){
            if(a[i]==1)b[i]=2;
            if(a[i]==2)b[i]=3;
            if(a[i]==3)b[i]=1;
        }
        printf("%d ",b[i]);
    }
    puts("");
}
int main(){
    int t;
    cin>>t;
    for(int i=1;i<=t;i++)solve();
}