COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/dheap.h @ 909:f112c18bc304

Last change on this file since 909:f112c18bc304 was 855:65a0521e744e, checked in by Peter Kovacs <kpeter@…>, 10 years ago

Rename heap structures (#301)

File size: 11.0 KB
RevLine 
[703]1/* -*- mode: C++; indent-tabs-mode: nil; -*-
[701]2 *
[703]3 * This file is a part of LEMON, a generic C++ optimization library.
[701]4 *
[703]5 * Copyright (C) 2003-2009
[701]6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
[855]19#ifndef LEMON_DHEAP_H
20#define LEMON_DHEAP_H
[701]21
[703]22///\ingroup heaps
[701]23///\file
[855]24///\brief D-ary heap implementation.
[701]25
26#include <vector>
27#include <utility>
28#include <functional>
29
30namespace lemon {
31
[703]32  /// \ingroup heaps
[701]33  ///
[855]34  ///\brief D-ary heap data structure.
[701]35  ///
[855]36  /// This class implements the \e D-ary \e heap data structure.
[703]37  /// It fully conforms to the \ref concepts::Heap "heap concept".
[701]38  ///
[855]39  /// The \ref DHeap "D-ary heap" is a generalization of the
[703]40  /// \ref BinHeap "binary heap" structure, its nodes have at most
[855]41  /// \c D children, instead of two.
42  /// \ref BinHeap and \ref QuadHeap are specialized implementations
43  /// of this structure for <tt>D=2</tt> and <tt>D=4</tt>, respectively.
[701]44  ///
[703]45  /// \tparam PR Type of the priorities of the items.
46  /// \tparam IM A read-writable item map with \c int values, used
47  /// internally to handle the cross references.
[855]48  /// \tparam D The degree of the heap, each node have at most \e D
[704]49  /// children. The default is 16. Powers of two are suggested to use
50  /// so that the multiplications and divisions needed to traverse the
51  /// nodes of the heap could be performed faster.
[703]52  /// \tparam CMP A functor class for comparing the priorities.
53  /// The default is \c std::less<PR>.
54  ///
55  ///\sa BinHeap
56  ///\sa FouraryHeap
57#ifdef DOXYGEN
[855]58  template <typename PR, typename IM, int D, typename CMP>
[703]59#else
[855]60  template <typename PR, typename IM, int D = 16,
[704]61            typename CMP = std::less<PR> >
[703]62#endif
[855]63  class DHeap {
[703]64  public:
65    /// Type of the item-int map.
66    typedef IM ItemIntMap;
67    /// Type of the priorities.
68    typedef PR Prio;
69    /// Type of the items stored in the heap.
70    typedef typename ItemIntMap::Key Item;
71    /// Type of the item-priority pairs.
72    typedef std::pair<Item,Prio> Pair;
73    /// Functor type for comparing the priorities.
74    typedef CMP Compare;
[701]75
[703]76    /// \brief Type to represent the states of the items.
[701]77    ///
[703]78    /// Each item has a state associated to it. It can be "in heap",
79    /// "pre-heap" or "post-heap". The latter two are indifferent from the
[701]80    /// heap's point of view, but may be useful to the user.
81    ///
[703]82    /// The item-int map must be initialized in such way that it assigns
83    /// \c PRE_HEAP (<tt>-1</tt>) to any element to be put in the heap.
[701]84    enum State {
[703]85      IN_HEAP = 0,    ///< = 0.
86      PRE_HEAP = -1,  ///< = -1.
87      POST_HEAP = -2  ///< = -2.
[701]88    };
89
90  private:
[703]91    std::vector<Pair> _data;
92    Compare _comp;
93    ItemIntMap &_iim;
[701]94
95  public:
[703]96    /// \brief Constructor.
[701]97    ///
[703]98    /// Constructor.
99    /// \param map A map that assigns \c int values to the items.
100    /// It is used internally to handle the cross references.
101    /// The assigned value must be \c PRE_HEAP (<tt>-1</tt>) for each item.
[855]102    explicit DHeap(ItemIntMap &map) : _iim(map) {}
[701]103
[703]104    /// \brief Constructor.
[701]105    ///
[703]106    /// Constructor.
107    /// \param map A map that assigns \c int values to the items.
108    /// It is used internally to handle the cross references.
109    /// The assigned value must be \c PRE_HEAP (<tt>-1</tt>) for each item.
110    /// \param comp The function object used for comparing the priorities.
[855]111    DHeap(ItemIntMap &map, const Compare &comp)
[704]112      : _iim(map), _comp(comp) {}
[703]113
114    /// \brief The number of items stored in the heap.
[701]115    ///
[703]116    /// This function returns the number of items stored in the heap.
117    int size() const { return _data.size(); }
[701]118
[703]119    /// \brief Check if the heap is empty.
120    ///
121    /// This function returns \c true if the heap is empty.
122    bool empty() const { return _data.empty(); }
[701]123
[703]124    /// \brief Make the heap empty.
[701]125    ///
[703]126    /// This functon makes the heap empty.
127    /// It does not change the cross reference map. If you want to reuse
128    /// a heap that is not surely empty, you should first clear it and
129    /// then you should set the cross reference map to \c PRE_HEAP
130    /// for each item.
131    void clear() { _data.clear(); }
[701]132
133  private:
[855]134    int parent(int i) { return (i-1)/D; }
135    int firstChild(int i) { return D*i+1; }
[701]136
137    bool less(const Pair &p1, const Pair &p2) const {
[703]138      return _comp(p1.second, p2.second);
[701]139    }
140
[703]141    void bubbleUp(int hole, Pair p) {
[701]142      int par = parent(hole);
[703]143      while( hole>0 && less(p,_data[par]) ) {
144        move(_data[par],hole);
[701]145        hole = par;
146        par = parent(hole);
147      }
148      move(p, hole);
149    }
150
[703]151    void bubbleDown(int hole, Pair p, int length) {
[701]152      if( length>1 ) {
[703]153        int child = firstChild(hole);
[855]154        while( child+D<=length ) {
[706]155          int min=child;
[855]156          for (int i=1; i<D; ++i) {
[706]157            if( less(_data[child+i], _data[min]) )
158              min=child+i;
159          }
160          if( !less(_data[min], p) )
[701]161            goto ok;
[706]162          move(_data[min], hole);
163          hole = min;
[703]164          child = firstChild(hole);
[701]165        }
[706]166        if ( child<length ) {
167          int min = child;
168          while (++child < length) {
169            if( less(_data[child], _data[min]) )
170              min=child;
171          }
172          if( less(_data[min], p) ) {
173            move(_data[min], hole);
174            hole = min;
175          }
176        }
[701]177      }
178    ok:
179      move(p, hole);
180    }
181
182    void move(const Pair &p, int i) {
[703]183      _data[i] = p;
184      _iim.set(p.first, i);
[701]185    }
186
187  public:
188    /// \brief Insert a pair of item and priority into the heap.
189    ///
[703]190    /// This function inserts \c p.first to the heap with priority
191    /// \c p.second.
[701]192    /// \param p The pair to insert.
[703]193    /// \pre \c p.first must not be stored in the heap.
[701]194    void push(const Pair &p) {
[703]195      int n = _data.size();
196      _data.resize(n+1);
197      bubbleUp(n, p);
[701]198    }
199
[703]200    /// \brief Insert an item into the heap with the given priority.
[701]201    ///
[703]202    /// This function inserts the given item into the heap with the
203    /// given priority.
[701]204    /// \param i The item to insert.
205    /// \param p The priority of the item.
[703]206    /// \pre \e i must not be stored in the heap.
[701]207    void push(const Item &i, const Prio &p) { push(Pair(i,p)); }
208
[703]209    /// \brief Return the item having minimum priority.
[701]210    ///
[703]211    /// This function returns the item having minimum priority.
212    /// \pre The heap must be non-empty.
213    Item top() const { return _data[0].first; }
[701]214
[703]215    /// \brief The minimum priority.
[701]216    ///
[703]217    /// This function returns the minimum priority.
218    /// \pre The heap must be non-empty.
219    Prio prio() const { return _data[0].second; }
[701]220
[703]221    /// \brief Remove the item having minimum priority.
[701]222    ///
[703]223    /// This function removes the item having minimum priority.
[701]224    /// \pre The heap must be non-empty.
225    void pop() {
[703]226      int n = _data.size()-1;
227      _iim.set(_data[0].first, POST_HEAP);
228      if (n>0) bubbleDown(0, _data[n], n);
229      _data.pop_back();
[701]230    }
231
[703]232    /// \brief Remove the given item from the heap.
[701]233    ///
[703]234    /// This function removes the given item from the heap if it is
235    /// already stored.
236    /// \param i The item to delete.
237    /// \pre \e i must be in the heap.
[701]238    void erase(const Item &i) {
[703]239      int h = _iim[i];
240      int n = _data.size()-1;
241      _iim.set(_data[h].first, POST_HEAP);
[701]242      if( h<n ) {
[703]243        if( less(_data[parent(h)], _data[n]) )
244          bubbleDown(h, _data[n], n);
[701]245        else
[703]246          bubbleUp(h, _data[n]);
[701]247      }
[703]248      _data.pop_back();
[701]249    }
250
[703]251    /// \brief The priority of the given item.
[701]252    ///
[703]253    /// This function returns the priority of the given item.
[701]254    /// \param i The item.
[703]255    /// \pre \e i must be in the heap.
[701]256    Prio operator[](const Item &i) const {
[703]257      int idx = _iim[i];
258      return _data[idx].second;
[701]259    }
260
[703]261    /// \brief Set the priority of an item or insert it, if it is
262    /// not stored in the heap.
[701]263    ///
[703]264    /// This method sets the priority of the given item if it is
265    /// already stored in the heap. Otherwise it inserts the given
266    /// item into the heap with the given priority.
[701]267    /// \param i The item.
268    /// \param p The priority.
269    void set(const Item &i, const Prio &p) {
[703]270      int idx = _iim[i];
[701]271      if( idx<0 )
272        push(i,p);
[703]273      else if( _comp(p, _data[idx].second) )
274        bubbleUp(idx, Pair(i,p));
[701]275      else
[703]276        bubbleDown(idx, Pair(i,p), _data.size());
[701]277    }
278
[703]279    /// \brief Decrease the priority of an item to the given value.
[701]280    ///
[703]281    /// This function decreases the priority of an item to the given value.
[701]282    /// \param i The item.
283    /// \param p The priority.
[703]284    /// \pre \e i must be stored in the heap with priority at least \e p.
[701]285    void decrease(const Item &i, const Prio &p) {
[703]286      int idx = _iim[i];
287      bubbleUp(idx, Pair(i,p));
[701]288    }
289
[703]290    /// \brief Increase the priority of an item to the given value.
[701]291    ///
[703]292    /// This function increases the priority of an item to the given value.
[701]293    /// \param i The item.
294    /// \param p The priority.
[703]295    /// \pre \e i must be stored in the heap with priority at most \e p.
[701]296    void increase(const Item &i, const Prio &p) {
[703]297      int idx = _iim[i];
298      bubbleDown(idx, Pair(i,p), _data.size());
[701]299    }
300
[703]301    /// \brief Return the state of an item.
[701]302    ///
[703]303    /// This method returns \c PRE_HEAP if the given item has never
304    /// been in the heap, \c IN_HEAP if it is in the heap at the moment,
305    /// and \c POST_HEAP otherwise.
306    /// In the latter case it is possible that the item will get back
307    /// to the heap again.
[701]308    /// \param i The item.
309    State state(const Item &i) const {
[703]310      int s = _iim[i];
[701]311      if (s>=0) s=0;
312      return State(s);
313    }
314
[703]315    /// \brief Set the state of an item in the heap.
[701]316    ///
[703]317    /// This function sets the state of the given item in the heap.
318    /// It can be used to manually clear the heap when it is important
319    /// to achive better time complexity.
[701]320    /// \param i The item.
321    /// \param st The state. It should not be \c IN_HEAP.
322    void state(const Item& i, State st) {
323      switch (st) {
[703]324        case POST_HEAP:
325        case PRE_HEAP:
326          if (state(i) == IN_HEAP) erase(i);
327          _iim[i] = st;
328          break;
329        case IN_HEAP:
330          break;
[701]331      }
332    }
333
[703]334    /// \brief Replace an item in the heap.
[701]335    ///
[703]336    /// This function replaces item \c i with item \c j.
337    /// Item \c i must be in the heap, while \c j must be out of the heap.
338    /// After calling this method, item \c i will be out of the
339    /// heap and \c j will be in the heap with the same prioriority
340    /// as item \c i had before.
[701]341    void replace(const Item& i, const Item& j) {
[703]342      int idx=_iim[i];
343      _iim.set(i, _iim[j]);
344      _iim.set(j, idx);
345      _data[idx].first=j;
[701]346    }
347
[855]348  }; // class DHeap
[701]349
350} // namespace lemon
351
[855]352#endif // LEMON_DHEAP_H
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