COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/bin_heap.h @ 2258:741995f3dbc4

Last change on this file since 2258:741995f3dbc4 was 2258:741995f3dbc4, checked in by Alpar Juttner, 13 years ago

Docfix.
maps.h is still very fuzzy.

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1/* -*- C++ -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library
4 *
5 * Copyright (C) 2003-2006
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
19#ifndef LEMON_BIN_HEAP_H
20#define LEMON_BIN_HEAP_H
21
22///\ingroup auxdat
23///\file
24///\brief Binary Heap implementation.
25
26#include <vector>
27#include <utility>
28#include <functional>
29
30namespace lemon {
31
32  /// \ingroup auxdat
33
34  /// A Binary Heap implementation.
35 
36  ///This class implements the \e binary \e heap data structure. A \e heap
37  ///is a data structure for storing items with specified values called \e
38  ///priorities in such a way that finding the item with minimum priority is
39  ///efficient. \c Compare specifies the ordering of the priorities. In a heap
40  ///one can change the priority of an item, add or erase an item, etc.
41  ///
42  ///\param Item Type of the items to be stored. 
43  ///\param Prio Type of the priority of the items.
44  ///\param ItemIntMap A read and writable Item int map, used internally
45  ///to handle the cross references.
46  ///\param Compare A class for the ordering of the priorities. The
47  ///default is \c std::less<Prio>.
48  ///
49  ///\sa FibHeap
50  ///\sa Dijkstra
51  template <typename Item, typename Prio, typename ItemIntMap,
52            typename Compare = std::less<Prio> >
53  class BinHeap {
54
55  public:
56    typedef Item                             ItemType;
57    typedef Prio                             PrioType;
58    typedef std::pair<ItemType,PrioType>     PairType;
59    typedef ItemIntMap                       ItemIntMapType;
60    typedef Compare                          PrioCompare;
61
62    /// \brief Type to represent the items states.
63    ///
64    /// Each Item element have a state associated to it. It may be "in heap",
65    /// "pre heap" or "post heap". The latter two are indifferent from the
66    /// heap's point of view, but may be useful to the user.
67    ///
68    /// The ItemIntMap \e should be initialized in such way that it maps
69    /// PRE_HEAP (-1) to any element to be put in the heap...
70    enum state_enum {
71      IN_HEAP = 0,
72      PRE_HEAP = -1,
73      POST_HEAP = -2
74    };
75
76  private:
77    std::vector<PairType> data;
78    Compare comp;
79    ItemIntMap &iim;
80
81  public:
82    /// \brief The constructor.
83    ///
84    /// The constructor.
85    /// \param _iim should be given to the constructor, since it is used
86    /// internally to handle the cross references. The value of the map
87    /// should be PRE_HEAP (-1) for each element.
88    explicit BinHeap(ItemIntMap &_iim) : iim(_iim) {}
89   
90    /// \brief The constructor.
91    ///
92    /// The constructor.
93    /// \param _iim should be given to the constructor, since it is used
94    /// internally to handle the cross references. The value of the map
95    /// should be PRE_HEAP (-1) for each element.
96    ///
97    /// \param _comp The comparator function object.
98    BinHeap(ItemIntMap &_iim, const Compare &_comp)
99      : iim(_iim), comp(_comp) {}
100
101
102    /// The number of items stored in the heap.
103    ///
104    /// \brief Returns the number of items stored in the heap.
105    int size() const { return data.size(); }
106   
107    /// \brief Checks if the heap stores no items.
108    ///
109    /// Returns \c true if and only if the heap stores no items.
110    bool empty() const { return data.empty(); }
111
112    /// \brief Make empty this heap.
113    ///
114    /// Make empty this heap. It does not change the cross reference map.
115    /// If you want to reuse what is not surely empty you should first clear
116    /// the heap and after that you should set the cross reference map for
117    /// each item to \c PRE_HEAP.
118    void clear() {
119      data.clear();
120    }
121
122  private:
123    static int parent(int i) { return (i-1)/2; }
124    static int second_child(int i) { return 2*i+2; }
125    bool less(const PairType &p1, const PairType &p2) const {
126      return comp(p1.second, p2.second);
127    }
128
129    int bubble_up(int hole, PairType p);
130    int bubble_down(int hole, PairType p, int length);
131
132    void move(const PairType &p, int i) {
133      data[i] = p;
134      iim.set(p.first, i);
135    }
136
137    void rmidx(int h) {
138      int n = data.size()-1;
139      if( h>=0 && h<=n ) {
140        iim.set(data[h].first, POST_HEAP);
141        if ( h<n ) {
142          bubble_down(h, data[n], n);
143        }
144        data.pop_back();
145      }
146    }
147
148  public:
149    /// \brief Insert a pair of item and priority into the heap.
150    ///
151    /// Adds \c p.first to the heap with priority \c p.second.
152    /// \param p The pair to insert.
153    void push(const PairType &p) {
154      int n = data.size();
155      data.resize(n+1);
156      bubble_up(n, p);
157    }
158
159    /// \brief Insert an item into the heap with the given heap.
160    ///   
161    /// Adds \c i to the heap with priority \c p.
162    /// \param i The item to insert.
163    /// \param p The priority of the item.
164    void push(const Item &i, const Prio &p) { push(PairType(i,p)); }
165
166    /// \brief Returns the item with minimum priority relative to \c Compare.
167    ///
168    /// This method returns the item with minimum priority relative to \c
169    /// Compare. 
170    /// \pre The heap must be nonempty. 
171    Item top() const {
172      return data[0].first;
173    }
174
175    /// \brief Returns the minimum priority relative to \c Compare.
176    ///
177    /// It returns the minimum priority relative to \c Compare.
178    /// \pre The heap must be nonempty.
179    Prio prio() const {
180      return data[0].second;
181    }
182
183    /// \brief Deletes the item with minimum priority relative to \c Compare.
184    ///
185    /// This method deletes the item with minimum priority relative to \c
186    /// Compare from the heap. 
187    /// \pre The heap must be non-empty. 
188    void pop() {
189      rmidx(0);
190    }
191
192    /// \brief Deletes \c i from the heap.
193    ///
194    /// This method deletes item \c i from the heap, if \c i was
195    /// already stored in the heap.
196    /// \param i The item to erase.
197    void erase(const Item &i) {
198      rmidx(iim[i]);
199    }
200
201   
202    /// \brief Returns the priority of \c i.
203    ///
204    /// This function returns the priority of item \c i. 
205    /// \pre \c i must be in the heap.
206    /// \param i The item.
207    Prio operator[](const Item &i) const {
208      int idx = iim[i];
209      return data[idx].second;
210    }
211
212    /// \brief \c i gets to the heap with priority \c p independently
213    /// if \c i was already there.
214    ///
215    /// This method calls \ref push(\c i, \c p) if \c i is not stored
216    /// in the heap and sets the priority of \c i to \c p otherwise.
217    /// \param i The item.
218    /// \param p The priority.
219    void set(const Item &i, const Prio &p) {
220      int idx = iim[i];
221      if( idx < 0 ) {
222        push(i,p);
223      }
224      else if( comp(p, data[idx].second) ) {
225        bubble_up(idx, PairType(i,p));
226      }
227      else {
228        bubble_down(idx, PairType(i,p), data.size());
229      }
230    }
231
232    /// \brief Decreases the priority of \c i to \c p.
233
234    /// This method decreases the priority of item \c i to \c p.
235    /// \pre \c i must be stored in the heap with priority at least \c
236    /// p relative to \c Compare.
237    /// \param i The item.
238    /// \param p The priority.
239    void decrease(const Item &i, const Prio &p) {
240      int idx = iim[i];
241      bubble_up(idx, PairType(i,p));
242    }
243   
244    /// \brief Increases the priority of \c i to \c p.
245    ///
246    /// This method sets the priority of item \c i to \c p.
247    /// \pre \c i must be stored in the heap with priority at most \c
248    /// p relative to \c Compare.
249    /// \param i The item.
250    /// \param p The priority.
251    void increase(const Item &i, const Prio &p) {
252      int idx = iim[i];
253      bubble_down(idx, PairType(i,p), data.size());
254    }
255
256    /// \brief Returns if \c item is in, has already been in, or has
257    /// never been in the heap.
258    ///
259    /// This method returns PRE_HEAP if \c item has never been in the
260    /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP
261    /// otherwise. In the latter case it is possible that \c item will
262    /// get back to the heap again.
263    /// \param i The item.
264    state_enum state(const Item &i) const {
265      int s = iim[i];
266      if( s>=0 )
267        s=0;
268      return state_enum(s);
269    }
270
271    /// \brief Sets the state of the \c item in the heap.
272    ///
273    /// Sets the state of the \c item in the heap. It can be used to
274    /// manually clear the heap when it is important to achive the
275    /// better time complexity.
276    /// \param i The item.
277    /// \param st The state. It should not be \c IN_HEAP.
278    void state(const Item& i, state_enum st) {
279      switch (st) {
280      case POST_HEAP:
281      case PRE_HEAP:
282        if (state(i) == IN_HEAP) {
283          erase(i);
284        }
285        iim[i] = st;
286        break;
287      case IN_HEAP:
288        break;
289      }
290    }
291
292  }; // class BinHeap
293
294 
295  template <typename K, typename V, typename M, typename C>
296  int BinHeap<K,V,M,C>::bubble_up(int hole, PairType p) {
297    int par = parent(hole);
298    while( hole>0 && less(p,data[par]) ) {
299      move(data[par],hole);
300      hole = par;
301      par = parent(hole);
302    }
303    move(p, hole);
304    return hole;
305  }
306
307  template <typename K, typename V, typename M, typename C>
308  int BinHeap<K,V,M,C>::bubble_down(int hole, PairType p, int length) {
309    int child = second_child(hole);
310    while(child < length) {
311      if( less(data[child-1], data[child]) ) {
312        --child;
313      }
314      if( !less(data[child], p) )
315        goto ok;
316      move(data[child], hole);
317      hole = child;
318      child = second_child(hole);
319    }
320    child--;
321    if( child<length && less(data[child], p) ) {
322      move(data[child], hole);
323      hole=child;
324    }
325  ok:
326    move(p, hole);
327    return hole;
328  }
329
330
331} // namespace lemon
332
333#endif // LEMON_BIN_HEAP_H
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