高级题解

#include<bits/stdc++.h>
using namespace std;
const int N=100001;
int n,m;
int main(){
set<int>a;
cin>>n;
for(int i=1;i<=n;++i){
int j;
cin>>j;
a.insert(j);
}
cout<<a.size()<<endl;
for(auto x:a) cout<<x<<" ";
return 0;
}