lemon/concepts/heap.h
author Peter Kovacs <kpeter@inf.elte.hu>
Thu, 12 Nov 2009 23:27:21 +0100
changeset 807 78071e00de00
parent 709 0747f332c478
child 817 b87f0504cdbe
permissions -rw-r--r--
Traits class + a named parameter for CapacityScaling (#180)
to specify the heap used in internal Dijkstra computations.
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/* -*- mode: C++; indent-tabs-mode: nil; -*-
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 *
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 * This file is a part of LEMON, a generic C++ optimization library.
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 *
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 * Copyright (C) 2003-2009
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 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
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 * (Egervary Research Group on Combinatorial Optimization, EGRES).
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 *
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 * Permission to use, modify and distribute this software is granted
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 * provided that this copyright notice appears in all copies. For
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 * precise terms see the accompanying LICENSE file.
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 *
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 * This software is provided "AS IS" with no warranty of any kind,
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 * express or implied, and with no claim as to its suitability for any
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 * purpose.
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 *
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 */
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#ifndef LEMON_CONCEPTS_HEAP_H
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#define LEMON_CONCEPTS_HEAP_H
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///\ingroup concept
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///\file
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///\brief The concept of heaps.
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#include <lemon/core.h>
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#include <lemon/concept_check.h>
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namespace lemon {
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  namespace concepts {
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    /// \addtogroup concept
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    /// @{
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    /// \brief The heap concept.
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    ///
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    /// This concept class describes the main interface of heaps.
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    /// The various \ref heaps "heap structures" are efficient
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    /// implementations of the abstract data type \e priority \e queue.
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    /// They store items with specified values called \e priorities
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    /// in such a way that finding and removing the item with minimum
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    /// priority are efficient. The basic operations are adding and
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    /// erasing items, changing the priority of an item, etc.
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    ///
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    /// Heaps are crucial in several algorithms, such as Dijkstra and Prim.
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    /// Any class that conforms to this concept can be used easily in such
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    /// algorithms.
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    ///
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    /// \tparam PR Type of the priorities of the items.
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    /// \tparam IM A read-writable item map with \c int values, used
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    /// internally to handle the cross references.
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    /// \tparam CMP A functor class for comparing the priorities.
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    /// The default is \c std::less<PR>.
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#ifdef DOXYGEN
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    template <typename PR, typename IM, typename CMP>
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#else
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    template <typename PR, typename IM, typename CMP = std::less<PR> >
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#endif
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    class Heap {
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    public:
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      /// Type of the item-int map.
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      typedef IM ItemIntMap;
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      /// Type of the priorities.
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      typedef PR Prio;
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      /// Type of the items stored in the heap.
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      typedef typename ItemIntMap::Key Item;
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      /// \brief Type to represent the states of the items.
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      ///
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      /// Each item has a state associated to it. It can be "in heap",
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      /// "pre-heap" or "post-heap". The latter two are indifferent from the
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      /// heap's point of view, but may be useful to the user.
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      ///
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      /// The item-int map must be initialized in such way that it assigns
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      /// \c PRE_HEAP (<tt>-1</tt>) to any element to be put in the heap.
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      enum State {
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        IN_HEAP = 0,    ///< = 0. The "in heap" state constant.
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        PRE_HEAP = -1,  ///< = -1. The "pre-heap" state constant.
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        POST_HEAP = -2  ///< = -2. The "post-heap" state constant.
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      };
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      /// \brief Constructor.
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      ///
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      /// Constructor.
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      /// \param map A map that assigns \c int values to keys of type
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      /// \c Item. It is used internally by the heap implementations to
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      /// handle the cross references. The assigned value must be
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      /// \c PRE_HEAP (<tt>-1</tt>) for each item.
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      explicit Heap(ItemIntMap &map) {}
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      /// \brief Constructor.
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      ///
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      /// Constructor.
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      /// \param map A map that assigns \c int values to keys of type
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      /// \c Item. It is used internally by the heap implementations to
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      /// handle the cross references. The assigned value must be
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      /// \c PRE_HEAP (<tt>-1</tt>) for each item.
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      /// \param comp The function object used for comparing the priorities.
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      explicit Heap(ItemIntMap &map, const CMP &comp) {}
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      /// \brief The number of items stored in the heap.
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      ///
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      /// This function returns the number of items stored in the heap.
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      int size() const { return 0; }
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      /// \brief Check if the heap is empty.
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      ///
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      /// This function returns \c true if the heap is empty.
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      bool empty() const { return false; }
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      /// \brief Make the heap empty.
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      ///
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      /// This functon makes the heap empty.
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      /// It does not change the cross reference map. If you want to reuse
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      /// a heap that is not surely empty, you should first clear it and
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      /// then you should set the cross reference map to \c PRE_HEAP
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      /// for each item.
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      void clear() {}
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      /// \brief Insert an item into the heap with the given priority.
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      ///
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      /// This function inserts the given item into the heap with the
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      /// given priority.
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      /// \param i The item to insert.
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      /// \param p The priority of the item.
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      /// \pre \e i must not be stored in the heap.
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      void push(const Item &i, const Prio &p) {}
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      /// \brief Return the item having minimum priority.
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      ///
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      /// This function returns the item having minimum priority.
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      /// \pre The heap must be non-empty.
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      Item top() const {}
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      /// \brief The minimum priority.
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      ///
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      /// This function returns the minimum priority.
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      /// \pre The heap must be non-empty.
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      Prio prio() const {}
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      /// \brief Remove the item having minimum priority.
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      ///
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      /// This function removes the item having minimum priority.
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      /// \pre The heap must be non-empty.
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      void pop() {}
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      /// \brief Remove the given item from the heap.
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      ///
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      /// This function removes the given item from the heap if it is
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      /// already stored.
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      /// \param i The item to delete.
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      /// \pre \e i must be in the heap.
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      void erase(const Item &i) {}
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      /// \brief The priority of the given item.
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      ///
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      /// This function returns the priority of the given item.
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      /// \param i The item.
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      /// \pre \e i must be in the heap.
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      Prio operator[](const Item &i) const {}
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      /// \brief Set the priority of an item or insert it, if it is
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      /// not stored in the heap.
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      ///
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      /// This method sets the priority of the given item if it is
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      /// already stored in the heap. Otherwise it inserts the given
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      /// item into the heap with the given priority.
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      ///
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      /// \param i The item.
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      /// \param p The priority.
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      void set(const Item &i, const Prio &p) {}
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      /// \brief Decrease the priority of an item to the given value.
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      ///
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      /// This function decreases the priority of an item to the given value.
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      /// \param i The item.
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      /// \param p The priority.
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      /// \pre \e i must be stored in the heap with priority at least \e p.
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      void decrease(const Item &i, const Prio &p) {}
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      /// \brief Increase the priority of an item to the given value.
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      ///
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      /// This function increases the priority of an item to the given value.
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      /// \param i The item.
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      /// \param p The priority.
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      /// \pre \e i must be stored in the heap with priority at most \e p.
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      void increase(const Item &i, const Prio &p) {}
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      /// \brief Return the state of an item.
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      ///
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      /// This method returns \c PRE_HEAP if the given item has never
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      /// been in the heap, \c IN_HEAP if it is in the heap at the moment,
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      /// and \c POST_HEAP otherwise.
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      /// In the latter case it is possible that the item will get back
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      /// to the heap again.
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      /// \param i The item.
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      State state(const Item &i) const {}
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      /// \brief Set the state of an item in the heap.
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      ///
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      /// This function sets the state of the given item in the heap.
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      /// It can be used to manually clear the heap when it is important
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      /// to achive better time complexity.
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      /// \param i The item.
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      /// \param st The state. It should not be \c IN_HEAP.
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      void state(const Item& i, State st) {}
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      template <typename _Heap>
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      struct Constraints {
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      public:
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        void constraints() {
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          typedef typename _Heap::Item OwnItem;
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          typedef typename _Heap::Prio OwnPrio;
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          typedef typename _Heap::State OwnState;
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          Item item;
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          Prio prio;
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          item=Item();
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          prio=Prio();
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          ignore_unused_variable_warning(item);
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          ignore_unused_variable_warning(prio);
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          OwnItem own_item;
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          OwnPrio own_prio;
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          OwnState own_state;
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          own_item=Item();
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          own_prio=Prio();
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          ignore_unused_variable_warning(own_item);
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          ignore_unused_variable_warning(own_prio);
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          ignore_unused_variable_warning(own_state);
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          _Heap heap1(map);
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          _Heap heap2 = heap1;
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          ignore_unused_variable_warning(heap1);
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          ignore_unused_variable_warning(heap2);
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          int s = heap.size();
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          ignore_unused_variable_warning(s);
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          bool e = heap.empty();
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          ignore_unused_variable_warning(e);
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          prio = heap.prio();
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          item = heap.top();
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          prio = heap[item];
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          own_prio = heap.prio();
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          own_item = heap.top();
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          own_prio = heap[own_item];
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          heap.push(item, prio);
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          heap.push(own_item, own_prio);
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          heap.pop();
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          heap.set(item, prio);
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          heap.decrease(item, prio);
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          heap.increase(item, prio);
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          heap.set(own_item, own_prio);
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          heap.decrease(own_item, own_prio);
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          heap.increase(own_item, own_prio);
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          heap.erase(item);
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          heap.erase(own_item);
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          heap.clear();
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          own_state = heap.state(own_item);
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          heap.state(own_item, own_state);
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          own_state = _Heap::PRE_HEAP;
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          own_state = _Heap::IN_HEAP;
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          own_state = _Heap::POST_HEAP;
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        }
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        _Heap& heap;
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        ItemIntMap& map;
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      };
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    };
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    /// @}
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  } // namespace lemon
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}
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#endif