COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/bin_heap.h @ 1993:2115143eceea

Last change on this file since 1993:2115143eceea was 1956:a055123339d5, checked in by Alpar Juttner, 14 years ago

Unified copyright notices

File size: 9.7 KB
Line 
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    // FIXME: stl-ben nem ezt hivjak value_type -nak, hanem a kovetkezot...
58    typedef Prio                             PrioType;
59    typedef std::pair<ItemType,PrioType>     PairType;
60    typedef ItemIntMap                       ItemIntMapType;
61    typedef Compare                          PrioCompare;
62
63    /// \brief Type to represent the items states.
64    ///
65    /// Each Item element have a state associated to it. It may be "in heap",
66    /// "pre heap" or "post heap". The latter two are indifferent from the
67    /// heap's point of view, but may be useful to the user.
68    ///
69    /// The ItemIntMap \e should be initialized in such way that it maps
70    /// PRE_HEAP (-1) to any element to be put in the heap...
71    enum state_enum {
72      IN_HEAP = 0,
73      PRE_HEAP = -1,
74      POST_HEAP = -2
75    };
76
77  private:
78    std::vector<PairType> data;
79    Compare comp;
80    ItemIntMap &iim;
81
82  public:
83    /// \brief The constructor.
84    ///
85    /// The constructor.
86    /// \param _iim should be given to the constructor, since it is used
87    /// internally to handle the cross references. The value of the map
88    /// should be PRE_HEAP (-1) for each element.
89    explicit BinHeap(ItemIntMap &_iim) : iim(_iim) {}
90   
91    /// \brief The constructor.
92    ///
93    /// The constructor.
94    /// \param _iim should be given to the constructor, since it is used
95    /// internally to handle the cross references. The value of the map
96    /// should be PRE_HEAP (-1) for each element.
97    ///
98    /// \param _comp The comparator function object.
99    BinHeap(ItemIntMap &_iim, const Compare &_comp)
100      : iim(_iim), comp(_comp) {}
101
102
103    /// The number of items stored in the heap.
104    ///
105    /// \brief Returns the number of items stored in the heap.
106    int size() const { return data.size(); }
107   
108    /// \brief Checks if the heap stores no items.
109    ///
110    /// Returns \c true if and only if the heap stores no items.
111    bool empty() const { return data.empty(); }
112
113    /// \brief Make empty this heap.
114    ///
115    /// Make empty this heap.
116    void clear() {
117      for (int i = 0; i < (int)data.size(); ++i) {
118        iim.set(data[i].first, POST_HEAP);
119      }
120      data.clear();
121    }
122
123  private:
124    static int parent(int i) { return (i-1)/2; }
125    static int second_child(int i) { return 2*i+2; }
126    bool less(const PairType &p1, const PairType &p2) const {
127      return comp(p1.second, p2.second);
128    }
129
130    int bubble_up(int hole, PairType p);
131    int bubble_down(int hole, PairType p, int length);
132
133    void move(const PairType &p, int i) {
134      data[i] = p;
135      iim.set(p.first, i);
136    }
137
138    void rmidx(int h) {
139      int n = data.size()-1;
140      if( h>=0 && h<=n ) {
141        iim.set(data[h].first, POST_HEAP);
142        if ( h<n ) {
143          bubble_down(h, data[n], n);
144        }
145        data.pop_back();
146      }
147    }
148
149  public:
150    /// \brief Insert a pair of item and priority into the heap.
151    ///
152    /// Adds \c p.first to the heap with priority \c p.second.
153    /// \param p The pair to insert.
154    void push(const PairType &p) {
155      int n = data.size();
156      data.resize(n+1);
157      bubble_up(n, p);
158    }
159
160    /// \brief Insert an item into the heap with the given heap.
161    ///   
162    /// Adds \c i to the heap with priority \c p.
163    /// \param i The item to insert.
164    /// \param p The priority of the item.
165    void push(const Item &i, const Prio &p) { push(PairType(i,p)); }
166
167    /// \brief Returns the item with minimum priority relative to \c Compare.
168    ///
169    /// This method returns the item with minimum priority relative to \c
170    /// Compare. 
171    /// \pre The heap must be nonempty. 
172    Item top() const {
173      return data[0].first;
174    }
175
176    /// \brief Returns the minimum priority relative to \c Compare.
177    ///
178    /// It returns the minimum priority relative to \c Compare.
179    /// \pre The heap must be nonempty.
180    Prio prio() const {
181      return data[0].second;
182    }
183
184    /// \brief Deletes the item with minimum priority relative to \c Compare.
185    ///
186    /// This method deletes the item with minimum priority relative to \c
187    /// Compare from the heap. 
188    /// \pre The heap must be non-empty. 
189    void pop() {
190      rmidx(0);
191    }
192
193    /// \brief Deletes \c i from the heap.
194    ///
195    /// This method deletes item \c i from the heap, if \c i was
196    /// already stored in the heap.
197    /// \param i The item to erase.
198    void erase(const Item &i) {
199      rmidx(iim[i]);
200    }
201
202   
203    /// \brief Returns the priority of \c i.
204    ///
205    /// This function returns the priority of item \c i. 
206    /// \pre \c i must be in the heap.
207    /// \param i The item.
208    Prio operator[](const Item &i) const {
209      int idx = iim[i];
210      return data[idx].second;
211    }
212
213    /// \brief \c i gets to the heap with priority \c p independently
214    /// if \c i was already there.
215    ///
216    /// This method calls \ref push(\c i, \c p) if \c i is not stored
217    /// in the heap and sets the priority of \c i to \c p otherwise.
218    /// \param i The item.
219    /// \param p The priority.
220    void set(const Item &i, const Prio &p) {
221      int idx = iim[i];
222      if( idx < 0 ) {
223        push(i,p);
224      }
225      else if( comp(p, data[idx].second) ) {
226        bubble_up(idx, PairType(i,p));
227      }
228      else {
229        bubble_down(idx, PairType(i,p), data.size());
230      }
231    }
232
233    /// \brief Decreases the priority of \c i to \c p.
234
235    /// This method decreases the priority of item \c i to \c p.
236    /// \pre \c i must be stored in the heap with priority at least \c
237    /// p relative to \c Compare.
238    /// \param i The item.
239    /// \param p The priority.
240    void decrease(const Item &i, const Prio &p) {
241      int idx = iim[i];
242      bubble_up(idx, PairType(i,p));
243    }
244   
245    /// \brief Increases the priority of \c i to \c p.
246    ///
247    /// This method sets the priority of item \c i to \c p.
248    /// \pre \c i must be stored in the heap with priority at most \c
249    /// p relative to \c Compare.
250    /// \param i The item.
251    /// \param p The priority.
252    void increase(const Item &i, const Prio &p) {
253      int idx = iim[i];
254      bubble_down(idx, PairType(i,p), data.size());
255    }
256
257    /// \brief Returns if \c item is in, has already been in, or has
258    /// never been in the heap.
259    ///
260    /// This method returns PRE_HEAP if \c item has never been in the
261    /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP
262    /// otherwise. In the latter case it is possible that \c item will
263    /// get back to the heap again.
264    /// \param i The item.
265    state_enum state(const Item &i) const {
266      int s = iim[i];
267      if( s>=0 )
268        s=0;
269      return state_enum(s);
270    }
271
272    /// \brief Sets the state of the \c item in the heap.
273    ///
274    /// Sets the state of the \c item in the heap. It can be used to
275    /// manually clear the heap when it is important to achive the
276    /// better time complexity.
277    /// \param i The item.
278    /// \param st The state. It should not be \c IN_HEAP.
279    void state(const Item& i, state_enum st) {
280      switch (st) {
281      case POST_HEAP:
282      case PRE_HEAP:
283        if (state(i) == IN_HEAP) {
284          erase(i);
285        }
286        iim[i] = st;
287        break;
288      case IN_HEAP:
289        break;
290      }
291    }
292
293  }; // class BinHeap
294
295 
296  template <typename K, typename V, typename M, typename C>
297  int BinHeap<K,V,M,C>::bubble_up(int hole, PairType p) {
298    int par = parent(hole);
299    while( hole>0 && less(p,data[par]) ) {
300      move(data[par],hole);
301      hole = par;
302      par = parent(hole);
303    }
304    move(p, hole);
305    return hole;
306  }
307
308  template <typename K, typename V, typename M, typename C>
309  int BinHeap<K,V,M,C>::bubble_down(int hole, PairType p, int length) {
310    int child = second_child(hole);
311    while(child < length) {
312      if( less(data[child-1], data[child]) ) {
313        --child;
314      }
315      if( !less(data[child], p) )
316        goto ok;
317      move(data[child], hole);
318      hole = child;
319      child = second_child(hole);
320    }
321    child--;
322    if( child<length && less(data[child], p) ) {
323      move(data[child], hole);
324      hole=child;
325    }
326  ok:
327    move(p, hole);
328    return hole;
329  }
330
331
332} // namespace lemon
333
334#endif // LEMON_BIN_HEAP_H
Note: See TracBrowser for help on using the repository browser.