COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/lemon/bin_heap.h @ 1359:1581f961cfaa

Last change on this file since 1359:1581f961cfaa was 1359:1581f961cfaa, checked in by Alpar Juttner, 15 years ago

Correct the english name of EGRES.

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1/* -*- C++ -*-
2 * src/lemon/bin_heap.h - Part of LEMON, a generic C++ optimization library
3 *
4 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
5 * (Egervary Research Group on Combinatorial Optimization, EGRES).
6 *
7 * Permission to use, modify and distribute this software is granted
8 * provided that this copyright notice appears in all copies. For
9 * precise terms see the accompanying LICENSE file.
10 *
11 * This software is provided "AS IS" with no warranty of any kind,
12 * express or implied, and with no claim as to its suitability for any
13 * purpose.
14 *
15 */
16
17#ifndef LEMON_BIN_HEAP_H
18#define LEMON_BIN_HEAP_H
19
20///\ingroup auxdat
21///\file
22///\brief Binary Heap implementation.
23
24#include <vector>
25#include <utility>
26#include <functional>
27
28namespace lemon {
29
30  /// \addtogroup auxdat
31  /// @{
32
33  /// A Binary Heap implementation.
34 
35  ///This class implements the \e binary \e heap data structure. A \e heap
36  ///is a data structure for storing items with specified values called \e
37  ///priorities in such a way that finding the item with minimum priority is
38  ///efficient. \c Compare specifies the ordering of the priorities. In a heap
39  ///one can change the priority of an item, add or erase an item, etc.
40  ///
41  ///\param Item Type of the items to be stored. 
42  ///\param Prio Type of the priority of the items.
43  ///\param ItemIntMap A read and writable Item int map, used internally
44  ///to handle the cross references.
45  ///\param Compare A class for the ordering of the priorities. The
46  ///default is \c std::less<Prio>.
47  ///
48  ///\sa FibHeap
49  ///\sa Dijkstra
50  template <typename Item, typename Prio, typename ItemIntMap,
51            typename Compare = std::less<Prio> >
52  class BinHeap {
53
54  public:
55    typedef Item                             ItemType;
56    // FIXME: stl-ben nem ezt hivjak value_type -nak, hanem a kovetkezot...
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  private:
113    static int parent(int i) { return (i-1)/2; }
114    static int second_child(int i) { return 2*i+2; }
115    bool less(const PairType &p1, const PairType &p2) const {
116      return comp(p1.second, p2.second);
117    }
118
119    int bubble_up(int hole, PairType p);
120    int bubble_down(int hole, PairType p, int length);
121
122    void move(const PairType &p, int i) {
123      data[i] = p;
124      iim.set(p.first, i);
125    }
126
127    void rmidx(int h) {
128      int n = data.size()-1;
129      if( h>=0 && h<=n ) {
130        iim.set(data[h].first, POST_HEAP);
131        if ( h<n ) {
132          bubble_down(h, data[n], n);
133        }
134        data.pop_back();
135      }
136    }
137
138  public:
139    /// \brief Insert a pair of item and priority into the heap.
140    ///
141    /// Adds \c p.first to the heap with priority \c p.second.
142    /// \param p The pair to insert.
143    void push(const PairType &p) {
144      int n = data.size();
145      data.resize(n+1);
146      bubble_up(n, p);
147    }
148
149    /// \brief Insert an item into the heap with the given heap.
150    ///   
151    /// Adds \c i to the heap with priority \c p.
152    /// \param i The item to insert.
153    /// \param p The priority of the item.
154    void push(const Item &i, const Prio &p) { push(PairType(i,p)); }
155
156    /// \brief Returns the item with minimum priority relative to \c Compare.
157    ///
158    /// This method returns the item with minimum priority relative to \c
159    /// Compare. 
160    /// \pre The heap must be nonempty. 
161    Item top() const {
162      return data[0].first;
163    }
164
165    /// \brief Returns the minimum priority relative to \c Compare.
166    ///
167    /// It returns the minimum priority relative to \c Compare.
168    /// \pre The heap must be nonempty.
169    Prio prio() const {
170      return data[0].second;
171    }
172
173    /// \brief Deletes the item with minimum priority relative to \c Compare.
174    ///
175    /// This method deletes the item with minimum priority relative to \c
176    /// Compare from the heap. 
177    /// \pre The heap must be non-empty. 
178    void pop() {
179      rmidx(0);
180    }
181
182    /// \brief Deletes \c i from the heap.
183    ///
184    /// This method deletes item \c i from the heap, if \c i was
185    /// already stored in the heap.
186    /// \param i The item to erase.
187    void erase(const Item &i) {
188      rmidx(iim[i]);
189    }
190
191   
192    /// \brief Returns the priority of \c i.
193    ///
194    /// This function returns the priority of item \c i. 
195    /// \pre \c i must be in the heap.
196    /// \param i The item.
197    Prio operator[](const Item &i) const {
198      int idx = iim[i];
199      return data[idx].second;
200    }
201
202    /// \brief \c i gets to the heap with priority \c p independently
203    /// if \c i was already there.
204    ///
205    /// This method calls \ref push(\c i, \c p) if \c i is not stored
206    /// in the heap and sets the priority of \c i to \c p otherwise.
207    /// \param i The item.
208    /// \param p The priority.
209    void set(const Item &i, const Prio &p) {
210      int idx = iim[i];
211      if( idx < 0 ) {
212        push(i,p);
213      }
214      else if( comp(p, data[idx].second) ) {
215        bubble_up(idx, PairType(i,p));
216      }
217      else {
218        bubble_down(idx, PairType(i,p), data.size());
219      }
220    }
221
222    /// \brief Decreases the priority of \c i to \c p.
223
224    /// This method decreases the priority of item \c i to \c p.
225    /// \pre \c i must be stored in the heap with priority at least \c
226    /// p relative to \c Compare.
227    /// \param i The item.
228    /// \param p The priority.
229    void decrease(const Item &i, const Prio &p) {
230      int idx = iim[i];
231      bubble_up(idx, PairType(i,p));
232    }
233   
234    /// \brief Increases the priority of \c i to \c p.
235    ///
236    /// This method sets the priority of item \c i to \c p.
237    /// \pre \c i must be stored in the heap with priority at most \c
238    /// p relative to \c Compare.
239    /// \param i The item.
240    /// \param p The priority.
241    void increase(const Item &i, const Prio &p) {
242      int idx = iim[i];
243      bubble_down(idx, PairType(i,p), data.size());
244    }
245
246    /// \brief Returns if \c item is in, has already been in, or has
247    /// never been in the heap.
248    ///
249    /// This method returns PRE_HEAP if \c item has never been in the
250    /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP
251    /// otherwise. In the latter case it is possible that \c item will
252    /// get back to the heap again.
253    /// \param i The item.
254    state_enum state(const Item &i) const {
255      int s = iim[i];
256      if( s>=0 )
257        s=0;
258      return state_enum(s);
259    }
260
261  }; // class BinHeap
262
263 
264  template <typename K, typename V, typename M, typename C>
265  int BinHeap<K,V,M,C>::bubble_up(int hole, PairType p) {
266    int par = parent(hole);
267    while( hole>0 && less(p,data[par]) ) {
268      move(data[par],hole);
269      hole = par;
270      par = parent(hole);
271    }
272    move(p, hole);
273    return hole;
274  }
275
276  template <typename K, typename V, typename M, typename C>
277  int BinHeap<K,V,M,C>::bubble_down(int hole, PairType p, int length) {
278    int child = second_child(hole);
279    while(child < length) {
280      if( less(data[child-1], data[child]) ) {
281        --child;
282      }
283      if( !less(data[child], p) )
284        goto ok;
285      move(data[child], hole);
286      hole = child;
287      child = second_child(hole);
288    }
289    child--;
290    if( child<length && less(data[child], p) ) {
291      move(data[child], hole);
292      hole=child;
293    }
294  ok:
295    move(p, hole);
296    return hole;
297  }
298
299  ///@}
300
301} // namespace lemon
302
303#endif // LEMON_BIN_HEAP_H
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