【題目敘述】http://codeforces.com/contest/1348/problem/B
#include <iostream>
#include <set>
#include <vector>
using namespace std;
int t, n, k, a[105];
set <int> st;
vector <int> v;
vector <int> ans;
int main() {
cin >> t;
while (t--){
cin >> n >> k;
st.clear();
v.clear();
for (int i = 0; i < n; i++){
cin >> a[i];
st.insert(a[i]);
}
for (auto i:st){
v.push_back(i);
}
if (v.size() < k){
for (int i = k-v.size(); i > 0; i--){
v.push_back(v.back());
}
}
ans.clear();
for (int i = 0; i < n; i++){
for (int j:v){
ans.push_back(j);
}
}
cout << ans.size() << "\n";
for (int i:ans){
cout << i << " ";
}
cout << "\n";
}
}