题解

#include<bits/stdc++.h>
using namespace std;
int a[110],b[100];
int main(){
int N, M;
cin >> N >> M;
vector<bool> arrived(N, false);
for (int i = 0; i < M; ++i) {
int num;
cin >> num;
arrived[num] = true;
}
vector<int> missing;
for (int i = 0; i < N; ++i) {
if (!arrived[i]) {
missing.push_back(i);
}
}
if (missing.empty()) {
cout << N << endl;
} else {
for (int i = 0; i < missing.size(); ++i) {
if (i > 0) {
cout << " ";
}
cout << missing[i];
}
cout << endl;
}

return 0;

}