题解

#include<iostream>
using namespace std;
int n;
int a[20]={};
void dfs(int k){
if(k==n+1){
for(int i=1;i<=n;i=i+1){
cout<<a[i]<<" ";
}
cout<<endl;
return ;
}
for(int i=1;i<=3;i=i+1){
a[k]=i;
dfs(k+1);
}
}
int main(){
cin>>n;
dfs(1);
}