lemon/bucket_heap.h
author Alpar Juttner <alpar@cs.elte.hu>
Thu, 05 Nov 2009 10:01:02 +0100
changeset 779 c160bf9f18ef
parent 682 bb8c4cd57900
child 709 0747f332c478
permissions -rw-r--r--
Merge
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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_BUCKET_HEAP_H
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#define LEMON_BUCKET_HEAP_H
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///\ingroup auxdat
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///\file
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///\brief Bucket Heap implementation.
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#include <vector>
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#include <utility>
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#include <functional>
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namespace lemon {
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  namespace _bucket_heap_bits {
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    template <bool MIN>
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    struct DirectionTraits {
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      static bool less(int left, int right) {
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        return left < right;
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      }
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      static void increase(int& value) {
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        ++value;
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      }
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    };
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    template <>
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    struct DirectionTraits<false> {
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      static bool less(int left, int right) {
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        return left > right;
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      }
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      static void increase(int& value) {
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        --value;
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      }
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    };
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  }
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  /// \ingroup auxdat
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  ///
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  /// \brief A Bucket Heap implementation.
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  ///
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  /// This class implements the \e bucket \e heap data structure. A \e heap
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  /// is a data structure for storing items with specified values called \e
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  /// priorities in such a way that finding the item with minimum priority is
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  /// efficient. The bucket heap is very simple implementation, it can store
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  /// only integer priorities and it stores for each priority in the
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  /// \f$ [0..C) \f$ range a list of items. So it should be used only when
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  /// the priorities are small. It is not intended to use as dijkstra heap.
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  ///
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  /// \param IM A read and write Item int map, used internally
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  /// to handle the cross references.
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  /// \param MIN If the given parameter is false then instead of the
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  /// minimum value the maximum can be retrivied with the top() and
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  /// prio() member functions.
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  template <typename IM, bool MIN = true>
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  class BucketHeap {
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  public:
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    /// \e
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    typedef typename IM::Key Item;
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    /// \e
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    typedef int Prio;
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    /// \e
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    typedef std::pair<Item, Prio> Pair;
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    /// \e
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    typedef IM ItemIntMap;
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  private:
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    typedef _bucket_heap_bits::DirectionTraits<MIN> Direction;
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  public:
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    /// \brief Type to represent the items states.
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    ///
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    /// Each Item element have a state associated to it. It may 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.
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      PRE_HEAP = -1,  ///< = -1.
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      POST_HEAP = -2  ///< = -2.
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    };
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  public:
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    /// \brief The constructor.
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    ///
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    /// The constructor.
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    /// \param map should be given to the constructor, since it is used
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    /// internally to handle the cross references. The value of the map
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    /// should be PRE_HEAP (-1) for each element.
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    explicit BucketHeap(ItemIntMap &map) : _iim(map), _minimum(0) {}
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    /// The number of items stored in the heap.
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    ///
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    /// \brief Returns the number of items stored in the heap.
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    int size() const { return _data.size(); }
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    /// \brief Checks if the heap stores no items.
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    ///
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    /// Returns \c true if and only if the heap stores no items.
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    bool empty() const { return _data.empty(); }
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    /// \brief Make empty this heap.
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    ///
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    /// Make empty this heap. It does not change the cross reference
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    /// map.  If you want to reuse a heap what is not surely empty you
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    /// should first clear the heap and after that you should set the
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    /// cross reference map for each item to \c PRE_HEAP.
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    void clear() {
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      _data.clear(); _first.clear(); _minimum = 0;
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    }
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  private:
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    void relocate_last(int idx) {
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      if (idx + 1 < int(_data.size())) {
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        _data[idx] = _data.back();
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        if (_data[idx].prev != -1) {
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          _data[_data[idx].prev].next = idx;
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        } else {
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          _first[_data[idx].value] = idx;
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        }
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        if (_data[idx].next != -1) {
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          _data[_data[idx].next].prev = idx;
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        }
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        _iim[_data[idx].item] = idx;
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      }
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      _data.pop_back();
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    }
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    void unlace(int idx) {
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      if (_data[idx].prev != -1) {
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        _data[_data[idx].prev].next = _data[idx].next;
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      } else {
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        _first[_data[idx].value] = _data[idx].next;
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      }
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      if (_data[idx].next != -1) {
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        _data[_data[idx].next].prev = _data[idx].prev;
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      }
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    }
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    void lace(int idx) {
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      if (int(_first.size()) <= _data[idx].value) {
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        _first.resize(_data[idx].value + 1, -1);
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      }
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      _data[idx].next = _first[_data[idx].value];
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      if (_data[idx].next != -1) {
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        _data[_data[idx].next].prev = idx;
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      }
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      _first[_data[idx].value] = idx;
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      _data[idx].prev = -1;
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    }
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  public:
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    /// \brief Insert a pair of item and priority into the heap.
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    ///
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    /// Adds \c p.first to the heap with priority \c p.second.
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    /// \param p The pair to insert.
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    void push(const Pair& p) {
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      push(p.first, p.second);
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    }
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    /// \brief Insert an item into the heap with the given priority.
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    ///
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    /// Adds \c i to the heap with priority \c p.
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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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    void push(const Item &i, const Prio &p) {
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      int idx = _data.size();
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      _iim[i] = idx;
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      _data.push_back(BucketItem(i, p));
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      lace(idx);
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      if (Direction::less(p, _minimum)) {
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        _minimum = p;
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      }
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    }
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    /// \brief Returns the item with minimum priority.
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    ///
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    /// This method returns the item with minimum priority.
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    /// \pre The heap must be nonempty.
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    Item top() const {
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      while (_first[_minimum] == -1) {
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        Direction::increase(_minimum);
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      }
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      return _data[_first[_minimum]].item;
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    }
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    /// \brief Returns the minimum priority.
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    ///
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    /// It returns the minimum priority.
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    /// \pre The heap must be nonempty.
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    Prio prio() const {
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      while (_first[_minimum] == -1) {
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        Direction::increase(_minimum);
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      }
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      return _minimum;
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    }
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    /// \brief Deletes the item with minimum priority.
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    ///
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    /// This method deletes the item with minimum priority from the heap.
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    /// \pre The heap must be non-empty.
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    void pop() {
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      while (_first[_minimum] == -1) {
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        Direction::increase(_minimum);
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      }
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      int idx = _first[_minimum];
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      _iim[_data[idx].item] = -2;
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      unlace(idx);
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      relocate_last(idx);
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    }
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    /// \brief Deletes \c i from the heap.
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    ///
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    /// This method deletes item \c i from the heap, if \c i was
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    /// already stored in the heap.
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    /// \param i The item to erase.
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    void erase(const Item &i) {
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      int idx = _iim[i];
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      _iim[_data[idx].item] = -2;
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      unlace(idx);
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      relocate_last(idx);
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    }
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    /// \brief Returns the priority of \c i.
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    ///
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    /// This function returns the priority of item \c i.
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    /// \pre \c i must be in the heap.
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    /// \param i The item.
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    Prio operator[](const Item &i) const {
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      int idx = _iim[i];
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      return _data[idx].value;
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    }
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    /// \brief \c i gets to the heap with priority \c p independently
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    /// if \c i was already there.
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    ///
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    /// This method calls \ref push(\c i, \c p) if \c i is not stored
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    /// in the heap and sets the priority of \c i to \c p otherwise.
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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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      int idx = _iim[i];
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      if (idx < 0) {
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        push(i, p);
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      } else if (Direction::less(p, _data[idx].value)) {
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        decrease(i, p);
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      } else {
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        increase(i, p);
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      }
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    }
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    /// \brief Decreases the priority of \c i to \c p.
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    ///
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    /// This method decreases the priority of item \c i to \c p.
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    /// \pre \c i must be stored in the heap with priority at least \c
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    /// p relative to \c Compare.
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    /// \param i The item.
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    /// \param p The priority.
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    void decrease(const Item &i, const Prio &p) {
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      int idx = _iim[i];
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      unlace(idx);
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      _data[idx].value = p;
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      if (Direction::less(p, _minimum)) {
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        _minimum = p;
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      }
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      lace(idx);
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    }
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    /// \brief Increases the priority of \c i to \c p.
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    ///
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    /// This method sets the priority of item \c i to \c p.
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    /// \pre \c i must be stored in the heap with priority at most \c
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    /// p relative to \c Compare.
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    /// \param i The item.
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    /// \param p The priority.
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    void increase(const Item &i, const Prio &p) {
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      int idx = _iim[i];
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      unlace(idx);
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      _data[idx].value = p;
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      lace(idx);
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    }
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    /// \brief Returns if \c item is in, has already been in, or has
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    /// never been in the heap.
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    ///
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    /// This method returns PRE_HEAP if \c item has never been in the
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    /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP
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    /// otherwise. In the latter case it is possible that \c item will
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    /// get back 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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      int idx = _iim[i];
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      if (idx >= 0) idx = 0;
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      return State(idx);
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    }
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    /// \brief Sets the state of the \c item in the heap.
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    ///
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    /// Sets the state of the \c item in the heap. It can be used to
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    /// manually clear the heap when it is important to achive the
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    /// 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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      switch (st) {
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      case POST_HEAP:
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      case PRE_HEAP:
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        if (state(i) == IN_HEAP) {
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          erase(i);
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        }
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        _iim[i] = st;
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        break;
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      case IN_HEAP:
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        break;
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      }
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    }
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  private:
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    struct BucketItem {
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      BucketItem(const Item& _item, int _value)
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        : item(_item), value(_value) {}
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      Item item;
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      int value;
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      int prev, next;
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    };
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    ItemIntMap& _iim;
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    std::vector<int> _first;
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    std::vector<BucketItem> _data;
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    mutable int _minimum;
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  }; // class BucketHeap
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  /// \ingroup auxdat
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  ///
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  /// \brief A Simplified Bucket Heap implementation.
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  ///
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  /// This class implements a simplified \e bucket \e heap data
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  /// structure.  It does not provide some functionality but it faster
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  /// and simplier data structure than the BucketHeap. The main
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  /// difference is that the BucketHeap stores for every key a double
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  /// linked list while this class stores just simple lists. In the
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  /// other way it does not support erasing each elements just the
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  /// minimal and it does not supports key increasing, decreasing.
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  ///
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  /// \param IM A read and write Item int map, used internally
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  /// to handle the cross references.
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  /// \param MIN If the given parameter is false then instead of the
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  /// minimum value the maximum can be retrivied with the top() and
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  /// prio() member functions.
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  ///
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  /// \sa BucketHeap
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  template <typename IM, bool MIN = true >
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  class SimpleBucketHeap {
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  public:
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    typedef typename IM::Key Item;
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    typedef int Prio;
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    typedef std::pair<Item, Prio> Pair;
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    typedef IM ItemIntMap;
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  private:
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    typedef _bucket_heap_bits::DirectionTraits<MIN> Direction;
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  public:
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    /// \brief Type to represent the items states.
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    ///
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    /// Each Item element have a state associated to it. It may 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.
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      PRE_HEAP = -1,  ///< = -1.
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      POST_HEAP = -2  ///< = -2.
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    };
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  public:
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    /// \brief The constructor.
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    ///
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    /// The constructor.
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    /// \param map should be given to the constructor, since it is used
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    /// internally to handle the cross references. The value of the map
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    /// should be PRE_HEAP (-1) for each element.
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    explicit SimpleBucketHeap(ItemIntMap &map)
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      : _iim(map), _free(-1), _num(0), _minimum(0) {}
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    /// \brief Returns the number of items stored in the heap.
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    ///
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    /// The number of items stored in the heap.
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    int size() const { return _num; }
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    /// \brief Checks if the heap stores no items.
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    ///
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    /// Returns \c true if and only if the heap stores no items.
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    bool empty() const { return _num == 0; }
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    /// \brief Make empty this heap.
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    ///
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    /// Make empty this heap. It does not change the cross reference
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    /// map.  If you want to reuse a heap what is not surely empty you
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    /// should first clear the heap and after that you should set the
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    /// cross reference map for each item to \c PRE_HEAP.
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    void clear() {
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      _data.clear(); _first.clear(); _free = -1; _num = 0; _minimum = 0;
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    }
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    /// \brief Insert a pair of item and priority into the heap.
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    ///
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    /// Adds \c p.first to the heap with priority \c p.second.
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    /// \param p The pair to insert.
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    void push(const Pair& p) {
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      push(p.first, p.second);
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    }
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    /// \brief Insert an item into the heap with the given priority.
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    ///
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    /// Adds \c i to the heap with priority \c p.
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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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    void push(const Item &i, const Prio &p) {
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      int idx;
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      if (_free == -1) {
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        idx = _data.size();
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        _data.push_back(BucketItem(i));
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      } else {
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        idx = _free;
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        _free = _data[idx].next;
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        _data[idx].item = i;
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      }
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      _iim[i] = idx;
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      if (p >= int(_first.size())) _first.resize(p + 1, -1);
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      _data[idx].next = _first[p];
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      _first[p] = idx;
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      if (Direction::less(p, _minimum)) {
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        _minimum = p;
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      }
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      ++_num;
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    }
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    /// \brief Returns the item with minimum priority.
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    ///
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    /// This method returns the item with minimum priority.
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    /// \pre The heap must be nonempty.
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   478
    Item top() const {
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   479
      while (_first[_minimum] == -1) {
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   480
        Direction::increase(_minimum);
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   481
      }
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   482
      return _data[_first[_minimum]].item;
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   483
    }
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    /// \brief Returns the minimum priority.
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    ///
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    /// It returns the minimum priority.
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   488
    /// \pre The heap must be nonempty.
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   489
    Prio prio() const {
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   490
      while (_first[_minimum] == -1) {
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   491
        Direction::increase(_minimum);
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   492
      }
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   493
      return _minimum;
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   494
    }
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   495
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    /// \brief Deletes the item with minimum priority.
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   497
    ///
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    /// This method deletes the item with minimum priority from the heap.
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    /// \pre The heap must be non-empty.
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   500
    void pop() {
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   501
      while (_first[_minimum] == -1) {
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   502
        Direction::increase(_minimum);
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   503
      }
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   504
      int idx = _first[_minimum];
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   505
      _iim[_data[idx].item] = -2;
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   506
      _first[_minimum] = _data[idx].next;
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   507
      _data[idx].next = _free;
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   508
      _free = idx;
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   509
      --_num;
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   510
    }
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   512
    /// \brief Returns the priority of \c i.
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   513
    ///
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    /// This function returns the priority of item \c i.
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   515
    /// \warning This operator is not a constant time function
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   516
    /// because it scans the whole data structure to find the proper
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   517
    /// value.
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   518
    /// \pre \c i must be in the heap.
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    /// \param i The item.
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   520
    Prio operator[](const Item &i) const {
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   521
      for (int k = 0; k < _first.size(); ++k) {
deba@683
   522
        int idx = _first[k];
deba@681
   523
        while (idx != -1) {
deba@683
   524
          if (_data[idx].item == i) {
deba@681
   525
            return k;
deba@681
   526
          }
deba@683
   527
          idx = _data[idx].next;
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   528
        }
deba@681
   529
      }
deba@681
   530
      return -1;
deba@681
   531
    }
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   532
deba@681
   533
    /// \brief Returns if \c item is in, has already been in, or has
deba@681
   534
    /// never been in the heap.
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   535
    ///
deba@681
   536
    /// This method returns PRE_HEAP if \c item has never been in the
deba@681
   537
    /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP
deba@681
   538
    /// otherwise. In the latter case it is possible that \c item will
deba@681
   539
    /// get back to the heap again.
deba@681
   540
    /// \param i The item.
deba@681
   541
    State state(const Item &i) const {
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   542
      int idx = _iim[i];
deba@681
   543
      if (idx >= 0) idx = 0;
deba@681
   544
      return State(idx);
deba@681
   545
    }
deba@681
   546
deba@681
   547
  private:
deba@681
   548
deba@681
   549
    struct BucketItem {
deba@681
   550
      BucketItem(const Item& _item)
deba@681
   551
        : item(_item) {}
deba@681
   552
deba@681
   553
      Item item;
deba@681
   554
      int next;
deba@681
   555
    };
deba@681
   556
deba@683
   557
    ItemIntMap& _iim;
deba@683
   558
    std::vector<int> _first;
deba@683
   559
    std::vector<BucketItem> _data;
deba@683
   560
    int _free, _num;
deba@683
   561
    mutable int _minimum;
deba@681
   562
deba@681
   563
  }; // class SimpleBucketHeap
deba@681
   564
deba@681
   565
}
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   566
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   567
#endif