Clone a Directed Graph

Node* clone(Node* root) {
  //TODO: Write - Your - Code
   return root;
}

struct Node {
  int data;
  list<Node*> neighbors;
  Node(int d) : data(d) {}
};
Node* clone_rec(Node* root, 
        unordered_map<Node*, 
        Node*>& nodes_completed) {
  
  if (root == nullptr) {
    return nullptr;
  }
  Node* pNew = new Node(root->data);
  nodes_completed[root] = pNew;
  
  for (Node* p : root->neighbors) {
    
    auto x = nodes_completed.find(p);
    
    if (x == nodes_completed.end()){
      pNew->neighbors.push_back(clone_rec(p, nodes_completed));
    } else {
      pNew->neighbors.push_back(x->second /*value*/);
    }
  }
  
  return pNew;
}
Node* clone(Node* root) {
  unordered_map<Node*, Node*> nodes_completed;
  return clone_rec(root, nodes_completed);
}
// this is un-directed graph i.e.
// if there is an edge from x to y
// that means there must be an edge from y to x
// and there is no edge from a node to itself
// hence there can maximim of (nodes * nodes - nodes) / 2 edgesin this graph
void create_test_graph_undirected(int nodes, int edges, vector<Node*>& vertices) {
  for (int i = 0; i < nodes; ++i) {
    vertices.push_back(new Node(i));
  }
  vector<pair<int, int>> all_edges;
  for (int i = 0; i < vertices.size(); ++i) {
    for (int j = i + 1; j < vertices.size(); ++j) {
      all_edges.push_back(pair<int, int>(i, j));
    }
  }
  std::random_shuffle(all_edges.begin(), all_edges.end());
  for (int i = 0; i < edges && i < all_edges.size(); ++i) {
    pair<int, int>& edge = all_edges[i];
    vertices[edge.first]->neighbors.push_back(vertices[edge.second]);
    vertices[edge.second]->neighbors.push_back(vertices[edge.first]);
  }
}
void print_graph(vector<Node*>& vertices) {
  for (Node* n : vertices) {
    cout << n->data << ": {";
    for (Node* t : n->neighbors) {
      cout << t->data << " ";
    }
    cout << "}" << endl;
  }
}
void print_graph(Node* root, unordered_set<Node*>& visited_nodes) {
  if (root == nullptr || visited_nodes.find(root) != visited_nodes.end()) {
    return;
  }
  visited_nodes.insert(root);
  cout << root->data << ": {";
  for (Node* n : root->neighbors) {
    cout << n->data << " ";
  }
  cout << "}" << endl;
  for (Node* n : root->neighbors) {
    print_graph(n, visited_nodes);
  }
}
void print_graph(Node* root) {
  unordered_set<Node*> visited_nodes;
  print_graph(root, visited_nodes);
}
int main() {
  vector<Node*> vertices;
  create_test_graph_undirected(7, 18, vertices);
  
  print_graph(vertices[0]);
  Node* cp = clone(vertices[0]);
  cout << endl << "After copy" << endl;
  print_graph(cp);
  
  return 0;
}