func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     int x;     cin >> n >> x;     std::vector<int> a;     std::vector<int> p(1e6 + 20, 0);     std::vector<int> xo;     xo.push_back(0);     p[x] = p[0] = 1;     for (int pi = 1; pi < (1 << n); pi++) {       if (p[pi]) continue;       a.push_back(pi ^ xo.back());       p[pi ^ x] = 1;       p[pi] = 1;       xo.push_back(pi);     }     cout << a.size() << endl;     if (a.size() != 0) {       for (int y : a) cout << y <<    ;       cout << endl;     }   }   