

在吗?
拿一个桶标记一下
#include <iostream>
using namespace std;
int _;
int __;
bool ___[100005];
int ____;
int _____;
int ______;
int main()
{
cin >> _ >> __;
for (int i = 0; _______ < __; _______++)
{
cin >> ____;
___[____] = true;
}
for (int j = 1; ______ <= _; ______++)
{
if (!___[______])
{
cout << ______ << endl;
}
}
return 0;
}