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/* -*- mode: C++; indent-tabs-mode: nil; -*-

 *

 * This file is a part of LEMON, a generic C++ optimization library.

 *

 * Copyright (C) 2003-2009

 * 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.

 *

 */

#ifndef LEMON_CONCEPTS_HEAP_H

#define LEMON_CONCEPTS_HEAP_H

///\ingroup concept

///\file

///\brief The concept of heaps.

#include <lemon/core.h>

#include <lemon/concept_check.h>

namespace lemon {

  namespace concepts {

    /// \addtogroup concept

    /// @{

    /// \brief The heap concept.

    ///

    /// This concept class describes the main interface of heaps.

    /// The various \ref heaps "heap structures" are efficient

    /// implementations of the abstract data type \e priority \e queue.

    /// They store items with specified values called \e priorities

    /// in such a way that finding and removing the item with minimum

    /// priority are efficient. The basic operations are adding and

    /// erasing items, changing the priority of an item, etc.

    ///

    /// Heaps are crucial in several algorithms, such as Dijkstra and Prim.

    /// Any class that conforms to this concept can be used easily in such

    /// algorithms.

    ///

    /// \tparam PR Type of the priorities of the items.

    /// \tparam IM A read-writable item map with \c int values, used

    /// internally to handle the cross references.

    /// \tparam CMP A functor class for comparing the priorities.

    /// The default is \c std::less<PR>.

#ifdef DOXYGEN

    template <typename PR, typename IM, typename CMP>

#else

    template <typename PR, typename IM, typename CMP = std::less<PR> >

#endif

    class Heap {

    public:

      /// Type of the item-int map.

      typedef IM ItemIntMap;

      /// Type of the priorities.

      typedef PR Prio;

      /// Type of the items stored in the heap.

      typedef typename ItemIntMap::Key Item;

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

      ///

      /// Each item has a state associated to it. It can be "in heap",

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

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

      ///

      /// The item-int map must be initialized in such way that it assigns

      /// \c PRE_HEAP (<tt>-1</tt>) to any element to be put in the heap.

      enum State {

        IN_HEAP = 0,    ///< = 0. The "in heap" state constant.

        PRE_HEAP = -1,  ///< = -1. The "pre-heap" state constant.

        POST_HEAP = -2  ///< = -2. The "post-heap" state constant.

      };

      /// \brief Constructor.

      ///

      /// Constructor.

      /// \param map A map that assigns \c int values to keys of type

      /// \c Item. It is used internally by the heap implementations to

      /// handle the cross references. The assigned value must be

      /// \c PRE_HEAP (<tt>-1</tt>) for each item.

      explicit Heap(ItemIntMap &map) {}

      /// \brief Constructor.

      ///

      /// Constructor.

      /// \param map A map that assigns \c int values to keys of type

      /// \c Item. It is used internally by the heap implementations to

      /// handle the cross references. The assigned value must be

      /// \c PRE_HEAP (<tt>-1</tt>) for each item.

      /// \param comp The function object used for comparing the priorities.

      explicit Heap(ItemIntMap &map, const CMP &comp) {}

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

      ///

      /// This function returns the number of items stored in the heap.

      int size() const { return 0; }

      /// \brief Check if the heap is empty.

      ///

      /// This function returns \c true if the heap is empty.

      bool empty() const { return false; }

      /// \brief Make the heap empty.

      ///

      /// This functon makes the heap empty.

      /// It does not change the cross reference map. If you want to reuse

      /// a heap that is not surely empty, you should first clear it and

      /// then you should set the cross reference map to \c PRE_HEAP

      /// for each item.

      void clear() {}

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

      ///

      /// This function inserts the given item into the heap with the

      /// given priority.

      /// \param i The item to insert.

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

      /// \pre \e i must not be stored in the heap.

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

      /// \brief Return the item having minimum priority.

      ///

      /// This function returns the item having minimum priority.

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

      /// \brief The minimum priority.

      ///

      /// This function returns the minimum priority.

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

      /// \brief Remove the item having minimum priority.

      ///

      /// This function removes the item having minimum priority.

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

      void pop() {}

      /// \brief Remove the given item from the heap.

      ///

      /// This function removes the given item from the heap if it is

      /// already stored.

      /// \param i The item to delete.

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

      void erase(const Item &i) {}

      /// \brief The priority of the given item.

      ///

      /// This function returns the priority of the given item.

      /// \param i The item.

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

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

      /// \brief Set the priority of an item or insert it, if it is

      /// not stored in the heap.

      ///

      /// This method sets the priority of the given item if it is

      /// already stored in the heap. Otherwise it inserts the given

      /// item into the heap with the given priority.

      ///

      /// \param i The item.

      /// \param p The priority.

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

      /// \brief Decrease the priority of an item to the given value.

      ///

      /// This function decreases the priority of an item to the given value.

      /// \param i The item.

      /// \param p The priority.

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

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

      /// \brief Increase the priority of an item to the given value.

      ///

      /// This function increases the priority of an item to the given value.

      /// \param i The item.

      /// \param p The priority.

      /// \pre \e i must be stored in the heap with priority at most \e p.

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

      /// \brief Return the state of an item.

      ///

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

      /// been in the heap, \c IN_HEAP if it is in the heap at the moment,

      /// and \c POST_HEAP otherwise.

      /// In the latter case it is possible that the item will get back

      /// to the heap again.

      /// \param i The item.

      State state(const Item &i) const {}

      /// \brief Set the state of an item in the heap.

      ///

      /// This function sets the state of the given item in the heap.

      /// It can be used to manually clear the heap when it is important

      /// to achive better time complexity.

      /// \param i The item.

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

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

      template <typename _Heap>

      struct Constraints {

      public:

        void constraints() {

          typedef typename _Heap::Item OwnItem;

          typedef typename _Heap::Prio OwnPrio;

          typedef typename _Heap::State OwnState;

          Item item;

          Prio prio;

          item=Item();

          prio=Prio();

          ignore_unused_variable_warning(item);

          ignore_unused_variable_warning(prio);

          OwnItem own_item;

          OwnPrio own_prio;

          OwnState own_state;

          own_item=Item();

          own_prio=Prio();

          ignore_unused_variable_warning(own_item);

          ignore_unused_variable_warning(own_prio);

          ignore_unused_variable_warning(own_state);

          _Heap heap1(map);

          _Heap heap2 = heap1;

          ignore_unused_variable_warning(heap1);

          ignore_unused_variable_warning(heap2);

          int s = heap.size();

          ignore_unused_variable_warning(s);

          bool e = heap.empty();

          ignore_unused_variable_warning(e);

          prio = heap.prio();

          item = heap.top();

          prio = heap[item];

          own_prio = heap.prio();

          own_item = heap.top();

          own_prio = heap[own_item];

          heap.push(item, prio);

          heap.push(own_item, own_prio);

          heap.pop();

          heap.set(item, prio);

          heap.decrease(item, prio);

          heap.increase(item, prio);

          heap.set(own_item, own_prio);

          heap.decrease(own_item, own_prio);

          heap.increase(own_item, own_prio);

          heap.erase(item);

          heap.erase(own_item);

          heap.clear();

          own_state = heap.state(own_item);

          heap.state(own_item, own_state);

          own_state = _Heap::PRE_HEAP;

          own_state = _Heap::IN_HEAP;

          own_state = _Heap::POST_HEAP;

        }

        _Heap& heap;

        ItemIntMap& map;

      };

    };

    /// @}

  } // namespace lemon

}

#endif