Language: C++

using namespace std;
 
typedef pair<int,int> II;
const int maxm = 18;
 
bool mark[1<<maxm];
 
vector<II> vt;
int main() {
 
	ios::sync_with_stdio(false);
	cin.tie(0);
	int m = 0;
	int k = 0;
	cin >> m >> k;
	if (k >= (1<<m)) {
		cout << -1;
		return 0;
	}
 
	if (m == 0) {
		cout << "0 0";
	} else {
		if (m == 1) {
			if (k == 1) {
				cout << -1;
				return 0;
			} else {
				cout <<"0 0 1 1";
				return 0;
 
			}
		}
		for(int i=1;i<(1<<m);i++) {
			if (!mark[i] && i != k) {
				vt.push_back({i, k ^  i});
				mark[i] = true;
				mark[k ^ i] = true;
			}		
		}
		vector<int> res;
		res.push_back(0);
		int cnt = 0;
		for(int i=0;i<vt.size();i++) {
			res.push_back(k);
			if (cnt ==0) res.push_back(0);
			cnt++;
			res.push_back(vt[i].first);
			res.push_back(vt[i].second);
			res.push_back(k);
			res.push_back(vt[i].second);
			res.push_back(vt[i].first);
			if (res.size() > (1<<(m+1))) break;
		}
 
		if (res.size() < (1<<(m+1))) {
		
		} else {
			for(int i=0;i<(1<<(m+1));i++) cout << res[i] <<" ";
		}
	}
	return 0;
}

Compiler output:
a.cc:3:9: error: 'pair' does not name a type
    3 | typedef pair<int,int> II;
      |         ^~~~
a.cc:8:1: error: 'vector' does not name a type
    8 | vector<II> vt;
      | ^~~~~~
a.cc: In function 'int main()':
a.cc:11:9: error: 'ios' has not been declared
   11 |         ios::sync_with_stdio(false);
      |         ^~~
a.cc:12:9: error: 'cin' was not declared in this scope
   12 |         cin.tie(0);
      |         ^~~
a.cc:1:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
  +++ |+#include <iostream>
    1 | using namespace std;
a.cc:17:17: error: 'cout' was not declared in this scope
   17 |                 cout << -1;
      |                 ^~~~
a.cc:17:17: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:22:17: error: 'cout' was not declared in this scope
   22 |                 cout << "0 0";
      |                 ^~~~
a.cc:22:17: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:26:33: error: 'cout' was not declared in this scope
   26 |                                 cout << -1;
      |                                 ^~~~
a.cc:26:33: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:29:33: error: 'cout' was not declared in this scope
   29 |                                 cout <<"0 0 1 1";
      |                                 ^~~~
a.cc:29:33: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:36:33: error: 'vt' was not declared in this scope
   36 |                                 vt.push_back({i, k ^  i});
      |                                 ^~
a.cc:41:17: error: 'vector' was not declared in this scope
   41 |                 vector<int> res;
      |                 ^~~~~~
a.cc:1:1: note: 'std::vector' is defined in header '<vector>'; this is probably fixable by adding '#include <vector>'
  +++ |+#include <vector>
    1 | using namespace std;
a.cc:41:24: error: expected primary-expression before 'int'
   41 |                 vector<int> res;
      |                        ^~~
a.cc:42:17: error: 'res' was not declared in this scope
   42 |                 res.push_back(0);
      |                 ^~~
a.cc:44:31: error: 'vt' was not declared in this scope
   44 |                 for(int i=0;i<vt.size();i++) {
      |                               ^~
a.cc:59:55: error: 'cout' was not declared in this scope
   59 |                         for(int i=0;i<(1<<(m+1));i++) cout << res[i] <<" ";
      |                                                       ^~~~
a.cc:59:55: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'