/* -*- C++ -*-

  * lemon/concept/heap.h - Part of LEMON, a generic C++ optimization library

  *

  * Copyright (C) 2006 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

  * (Egervary Research Group on Combinatorial Optimization, EGRES).

  *

  * Permission to use, modify and distribute this software is granted

  * provided that this copyright notice appears in all copies. For

  * precise terms see the accompanying LICENSE file.

  *

  * This software is provided "AS IS" with no warranty of any kind,

  * express or implied, and with no claim as to its suitability for any

  * purpose.

  *

  */

 ///\ingroup concept

 ///\file

 ///\brief Classes for representing heaps.

 ///

 #ifndef LEMON_CONCEPT_HEAP_H

 #define LEMON_CONCEPT_HEAP_H

 #include <lemon/invalid.h>

 namespace lemon {

   namespace concept {

     /// \addtogroup concept

     /// @{

     /// \brief A concept structure describes the main interface of heaps.

     ///

     /// A concept structure describes the main interface of heaps.

     ///

     template <typename Item, typename Prio, typename ItemIntMap>

     class Heap {

     public:

       /// \brief Type to represent the items states.

       ///

       /// Each Item element have a state associated to it. It may be "in heap",

       /// "pre heap" or "post heap". The later two are indifferent from the

       /// heap's point of view, but may be useful to the user.

       ///

       /// The ItemIntMap _should_ be initialized in such way, that it maps

       /// PRE_HEAP (-1) to any element to be put in the heap...

       enum state_enum {

 	IN_HEAP = 0,

 	PRE_HEAP = -1,

 	POST_HEAP = -2

       };

       /// \brief The constructor.

       ///

       /// The constructor.

       /// \param _iim should be given to the constructor, since it is used

       /// internally to handle the cross references. The value of the map

       /// should be PRE_HEAP (-1) for each element.

       explicit Heap(ItemIntMap &_iim) {}

       /// \brief The number of items stored in the heap.

       ///

       /// Returns the number of items stored in the heap.

       int size() const { return 0; }

       /// \brief Checks if the heap stores no items.

       ///

       /// Returns \c true if and only if the heap stores no items.

       bool empty() const { return false; }

       /// \brief Makes empty this heap.

       ///

       /// Makes this heap empty.

       void clear();

       /// \brief Insert an item into the heap with the given heap.

       ///    

       /// Adds \c i to the heap with priority \c p. 

       /// \param i The item to insert.

       /// \param p The priority of the item.

       void push(const Item &i, const Prio &p) {}

       /// \brief Returns the item with minimum priority.

       ///

       /// This method returns the item with minimum priority.  

       /// \pre The heap must be nonempty.  

       Item top() const {}

       /// \brief Returns the minimum priority.

       ///

       /// It returns the minimum priority.

       /// \pre The heap must be nonempty.

       Prio prio() const {}

       /// \brief Deletes the item with minimum priority.

       ///

       /// This method deletes the item with minimum priority.

       /// \pre The heap must be non-empty.  

       void pop() {}

       /// \brief Deletes \c i from the heap.

       ///

       /// This method deletes item \c i from the heap, if \c i was

       /// already stored in the heap.

       /// \param i The item to erase. 

       void erase(const Item &i) {}

       /// \brief Returns the priority of \c i.

       ///

       /// This function returns the priority of item \c i.  

       /// \pre \c i must be in the heap.

       /// \param i The item.

       Prio operator[](const Item &i) const {}

       /// \brief \c i gets to the heap with priority \c p independently 

       /// if \c i was already there.

       ///

       /// This method calls \ref push(\c i, \c p) if \c i is not stored

       /// in the heap and sets the priority of \c i to \c p otherwise.

       /// It may throw an \e UnderFlowPriorityException. 

       /// \param i The item.

       /// \param p The priority.

       void set(const Item &i, const Prio &p) {}

       /// \brief Decreases the priority of \c i to \c p.

       ///

       /// This method decreases the priority of item \c i to \c p.

       /// \pre \c i must be stored in the heap with priority at least \c p.

       /// \param i The item.

       /// \param p The priority.

       void decrease(const Item &i, const Prio &p) {}

       /// \brief Increases the priority of \c i to \c p.

       ///

       /// This method sets the priority of item \c i to \c p. 

       /// \pre \c i must be stored in the heap with priority at most \c

       /// p relative to \c Compare.

       /// \param i The item.

       /// \param p The priority.

       void increase(const Item &i, const Prio &p) {}

       /// \brief Returns if \c item is in, has already been in, or has 

       /// never been in the heap.

       ///

       /// This method returns PRE_HEAP if \c item has never been in the

       /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP

       /// otherwise. In the latter case it is possible that \c item will

       /// get back to the heap again.

       /// \param i The item.

       state_enum state(const Item &i) const {}

       /// \brief Sets the state of the \c item in the heap.

       ///

       /// Sets the state of the \c item in the heap. It can be used to

       /// manually clear the heap when it is important to achive the

       /// better time complexity.

       /// \param i The item.

       /// \param st The state. It should not be \c IN_HEAP. 

       void state(const Item& i, state_enum st) {}

       template <typename _Heap>

       struct Constraints {

       public:

 	void constraints() {

 	  Item item;

 	  Prio prio;

 	  item=Item();

 	  prio=Prio();

 	  ignore_unused_variable_warning(item);

 	  ignore_unused_variable_warning(prio);

 	  typedef typename _Heap::state_enum state_enum;

 	  state_enum state;

 	  ignore_unused_variable_warning(state);

 	  _Heap heap1 = _Heap(map);

 	  ignore_unused_variable_warning(heap1);

 	  heap.push(item, prio);

 	  prio = heap.prio();

 	  item = heap.top();

 	  heap.pop();

 	  heap.set(item, prio);

 	  heap.decrease(item, prio);

 	  heap.increase(item, prio);

 	  prio = heap[item];

 	  heap.erase(item);

 	  state = heap.state(item);

 	  state = _Heap::PRE_HEAP;

 	  state = _Heap::IN_HEAP;

 	  state = _Heap::POST_HEAP;

 	  heap.clear();

 	}

 	_Heap& heap;

 	ItemIntMap& map;

 	Constraints() : heap(0), map(0) {}

       };

     };

     /// @}

   } // namespace lemon

 }

 #endif // LEMON_CONCEPT_PATH_H