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  1.     #include <iostream>
  2.     #include <array>
  3.     #include <vector>
  4.     #include <cassert>
  5.  
  6.     enum Direction {
  7.         North, East, West, South
  8.     };
  9.     enum { NumDirections = static_cast<int>(South + 1) };
  10.  
  11.     constexpr Direction reciprocalDirection(Direction dir)
  12.     {
  13.         // North :- 3 - 0 = 3 -> South
  14.         // East  :- 3 - 1 = 2 -> West
  15.         // West  :- 3 - 2 = 1 -> East
  16.         // South :- 3 - 3 = 0 -> North
  17.         return static_cast<Direction>(
  18.             (NumDirections - 1) - static_cast<unsigned int>(dir)
  19.         );
  20.     }
  21.  
  22.     struct Link
  23.     {
  24.         struct Room* m_room;        // struct needed to forward-declare
  25.         Link* m_reciprocal;         // The link back to us.
  26.  
  27.         Link() : m_room(nullptr), m_reciprocal(nullptr) {}
  28.  
  29.         operator bool() const { return m_room != nullptr; }
  30.  
  31.         static void Binder(Room* lhsRoom_, Link* lhsLink_, Link* rhsLink_, Room* rhsRoom_)
  32.         {
  33.             lhsLink_->m_room = rhsRoom_;
  34.             lhsLink_->m_reciprocal = rhsLink_;
  35.             rhsLink_->m_reciprocal = lhsLink_;
  36.             rhsLink_->m_room = lhsRoom_;
  37.         }
  38.  
  39.         void unbind()
  40.         {
  41.             if (m_room) {
  42.                 m_room = m_reciprocal->m_room = nullptr;
  43.                 m_reciprocal->m_reciprocal = nullptr;
  44.                 m_reciprocal = nullptr;
  45.             }
  46.         }
  47.  
  48.         ~Link() { unbind(); }
  49.     };
  50.  
  51.     struct Room
  52.     {
  53.         using Links = std::array<Link, NumDirections>;
  54.  
  55. 		template<typename T>
  56.         Room(T&& name_) : m_name(std::forward<T>(name_))
  57.         {
  58.         	std::cout << "Created Room(" << m_name << ") @ " << (void*)this << "\n";
  59.         }
  60.  
  61.         //! Indicates that from this room, in direction dir_, is room_
  62.         void link(Direction dir_, Room* room_);
  63.  
  64.         ~Room();
  65.  
  66.         const Room* link(Direction dir_) const { return m_links[dir_].m_room; }
  67.         Room* link(Direction dir_) { return m_links[dir_].m_room; }
  68.  
  69.         const std::string& name() const { return m_name; }
  70.  
  71.     private:
  72.     	std::string m_name;
  73.         Links m_links;
  74.     };
  75.  
  76.     std::ostream& operator<<(std::ostream& os, const Room& rm)
  77.     {
  78.     	os << "Room(" << rm.name() << ") @ " << (void*)(&rm);
  79.     	return os;
  80.     }
  81.  
  82.     int main()
  83.     {
  84.         Room* firstRoom = new Room("lobby");
  85.  
  86.         Room* newRoom = new Room("office");
  87.         firstRoom->link(North, newRoom);
  88.  
  89.         firstRoom->link(South, new Room("bedroom"));
  90.         firstRoom->link(West, new Room("bathroom"));
  91.  
  92.         newRoom->link(East, new Room("closet"));
  93.  
  94.         delete firstRoom;
  95.     }
  96.  
  97.     void Room::link(Direction dir_, Room* room_)
  98.     {
  99.         Direction opposite = reciprocalDirection(dir_);
  100.         std::cout << "Linking " << *room_ << " to " << *this
  101.         	<< " " << dir_ << ":" << opposite << "\n";
  102.         Link::Binder(this, &m_links[dir_], &room_->m_links[opposite], room_);
  103.     }
  104.  
  105.     Room::~Room()
  106.     {
  107.         static size_t depth = 0;
  108.         ++depth;
  109.  
  110.         std::string indent(depth, '|');
  111.  
  112.         std::cout << indent << "~" << *this << "\n";
  113.  
  114.         std::vector<Room*> unlinked;
  115.         for (auto& link: m_links) {
  116.             if (link) {
  117.                 if (link.m_room != this)
  118.                     unlinked.push_back(link.m_room);
  119.                 std::cout << indent << "Unlinked " << *link.m_room << " from " << *this << "\n";
  120.                 link.unbind();
  121.             }
  122.         }
  123.  
  124.         for (Room* room : unlinked) {
  125.             delete room;
  126.         }
  127.  
  128.         --depth;
  129.     }
  130.  
Success #stdin #stdout 0s 3276KB
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stdin
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Standard input is empty
stdout
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Created Room(lobby) @ 0x9730008
Created Room(office) @ 0x9730048
Linking Room(office) @ 0x9730048 to Room(lobby) @ 0x9730008 0:3
Created Room(bedroom) @ 0x9730088
Linking Room(bedroom) @ 0x9730088 to Room(lobby) @ 0x9730008 3:0
Created Room(bathroom) @ 0x97300c8
Linking Room(bathroom) @ 0x97300c8 to Room(lobby) @ 0x9730008 2:1
Created Room(closet) @ 0x9730110
Linking Room(closet) @ 0x9730110 to Room(office) @ 0x9730048 1:2
|~Room(lobby) @ 0x9730008
|Unlinked Room(office) @ 0x9730048 from Room(lobby) @ 0x9730008
|Unlinked Room(bathroom) @ 0x97300c8 from Room(lobby) @ 0x9730008
|Unlinked Room(bedroom) @ 0x9730088 from Room(lobby) @ 0x9730008
||~Room(office) @ 0x9730048
||Unlinked Room(closet) @ 0x9730110 from Room(office) @ 0x9730048
|||~Room(closet) @ 0x9730110
||~Room(bathroom) @ 0x97300c8
||~Room(bedroom) @ 0x9730088
https://ideone.com/jAqWX9
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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