1 /* -*- mode: C++; indent-tabs-mode: nil; -*-
3 * This file is a part of LEMON, a generic C++ optimization library.
5 * Copyright (C) 2003-2009
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
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.
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
19 #ifndef LEMON_FOURARY_HEAP_H
20 #define LEMON_FOURARY_HEAP_H
24 ///\brief Fourary heap implementation.
34 ///\brief Fourary heap data structure.
36 /// This class implements the \e fourary \e heap data structure.
37 /// It fully conforms to the \ref concepts::Heap "heap concept".
39 /// The fourary heap is a specialization of the \ref KaryHeap "K-ary heap"
40 /// for <tt>K=4</tt>. It is similar to the \ref BinHeap "binary heap",
41 /// but its nodes have at most four children, instead of two.
43 /// \tparam PR Type of the priorities of the items.
44 /// \tparam IM A read-writable item map with \c int values, used
45 /// internally to handle the cross references.
46 /// \tparam CMP A functor class for comparing the priorities.
47 /// The default is \c std::less<PR>.
52 template <typename PR, typename IM, typename CMP>
54 template <typename PR, typename IM, typename CMP = std::less<PR> >
58 /// Type of the item-int map.
59 typedef IM ItemIntMap;
60 /// Type of the priorities.
62 /// Type of the items stored in the heap.
63 typedef typename ItemIntMap::Key Item;
64 /// Type of the item-priority pairs.
65 typedef std::pair<Item,Prio> Pair;
66 /// Functor type for comparing the priorities.
69 /// \brief Type to represent the states of the items.
71 /// Each item has a state associated to it. It can be "in heap",
72 /// "pre-heap" or "post-heap". The latter two are indifferent from the
73 /// heap's point of view, but may be useful to the user.
75 /// The item-int map must be initialized in such way that it assigns
76 /// \c PRE_HEAP (<tt>-1</tt>) to any element to be put in the heap.
78 IN_HEAP = 0, ///< = 0.
79 PRE_HEAP = -1, ///< = -1.
80 POST_HEAP = -2 ///< = -2.
84 std::vector<Pair> _data;
89 /// \brief Constructor.
92 /// \param map A map that assigns \c int values to the items.
93 /// It is used internally to handle the cross references.
94 /// The assigned value must be \c PRE_HEAP (<tt>-1</tt>) for each item.
95 explicit FouraryHeap(ItemIntMap &map) : _iim(map) {}
97 /// \brief Constructor.
100 /// \param map A map that assigns \c int values to the items.
101 /// It is used internally to handle the cross references.
102 /// The assigned value must be \c PRE_HEAP (<tt>-1</tt>) for each item.
103 /// \param comp The function object used for comparing the priorities.
104 FouraryHeap(ItemIntMap &map, const Compare &comp)
105 : _iim(map), _comp(comp) {}
107 /// \brief The number of items stored in the heap.
109 /// This function returns the number of items stored in the heap.
110 int size() const { return _data.size(); }
112 /// \brief Check if the heap is empty.
114 /// This function returns \c true if the heap is empty.
115 bool empty() const { return _data.empty(); }
117 /// \brief Make the heap empty.
119 /// This functon makes the heap empty.
120 /// It does not change the cross reference map. If you want to reuse
121 /// a heap that is not surely empty, you should first clear it and
122 /// then you should set the cross reference map to \c PRE_HEAP
124 void clear() { _data.clear(); }
127 static int parent(int i) { return (i-1)/4; }
128 static int firstChild(int i) { return 4*i+1; }
130 bool less(const Pair &p1, const Pair &p2) const {
131 return _comp(p1.second, p2.second);
134 int findMin(const int child, const int length) {
136 if( child+3<length ) {
137 if( less(_data[child+3], _data[min]) )
139 if( less(_data[child+2], _data[min]) )
141 if( less(_data[child+1], _data[min]) )
144 else if( child+2<length ) {
145 if( less(_data[child+2], _data[min]) )
147 if( less(_data[child+1], _data[min]) )
150 else if( child+1<length ) {
151 if( less(_data[child+1], _data[min]) )
157 void bubbleUp(int hole, Pair p) {
158 int par = parent(hole);
159 while( hole>0 && less(p,_data[par]) ) {
160 move(_data[par],hole);
167 void bubbleDown(int hole, Pair p, int length) {
168 int child = firstChild(hole);
169 while( child<length && length>1 ) {
170 child = findMin(child,length);
171 if( !less(_data[child], p) )
173 move(_data[child], hole);
175 child = firstChild(hole);
181 void move(const Pair &p, int i) {
183 _iim.set(p.first, i);
187 /// \brief Insert a pair of item and priority into the heap.
189 /// This function inserts \c p.first to the heap with priority
191 /// \param p The pair to insert.
192 /// \pre \c p.first must not be stored in the heap.
193 void push(const Pair &p) {
194 int n = _data.size();
199 /// \brief Insert an item into the heap with the given priority.
201 /// This function inserts the given item into the heap with the
203 /// \param i The item to insert.
204 /// \param p The priority of the item.
205 /// \pre \e i must not be stored in the heap.
206 void push(const Item &i, const Prio &p) { push(Pair(i,p)); }
208 /// \brief Return the item having minimum priority.
210 /// This function returns the item having minimum priority.
211 /// \pre The heap must be non-empty.
212 Item top() const { return _data[0].first; }
214 /// \brief The minimum priority.
216 /// This function returns the minimum priority.
217 /// \pre The heap must be non-empty.
218 Prio prio() const { return _data[0].second; }
220 /// \brief Remove the item having minimum priority.
222 /// This function removes the item having minimum priority.
223 /// \pre The heap must be non-empty.
225 int n = _data.size()-1;
226 _iim.set(_data[0].first, POST_HEAP);
227 if (n>0) bubbleDown(0, _data[n], n);
231 /// \brief Remove the given item from the heap.
233 /// This function removes the given item from the heap if it is
235 /// \param i The item to delete.
236 /// \pre \e i must be in the heap.
237 void erase(const Item &i) {
239 int n = _data.size()-1;
240 _iim.set(_data[h].first, POST_HEAP);
242 if( less(_data[parent(h)], _data[n]) )
243 bubbleDown(h, _data[n], n);
245 bubbleUp(h, _data[n]);
250 /// \brief The priority of the given item.
252 /// This function returns the priority of the given item.
253 /// \param i The item.
254 /// \pre \e i must be in the heap.
255 Prio operator[](const Item &i) const {
257 return _data[idx].second;
260 /// \brief Set the priority of an item or insert it, if it is
261 /// not stored in the heap.
263 /// This method sets the priority of the given item if it is
264 /// already stored in the heap. Otherwise it inserts the given
265 /// item into the heap with the given priority.
266 /// \param i The item.
267 /// \param p The priority.
268 void set(const Item &i, const Prio &p) {
272 else if( _comp(p, _data[idx].second) )
273 bubbleUp(idx, Pair(i,p));
275 bubbleDown(idx, Pair(i,p), _data.size());
278 /// \brief Decrease the priority of an item to the given value.
280 /// This function decreases the priority of an item to the given value.
281 /// \param i The item.
282 /// \param p The priority.
283 /// \pre \e i must be stored in the heap with priority at least \e p.
284 void decrease(const Item &i, const Prio &p) {
286 bubbleUp(idx, Pair(i,p));
289 /// \brief Increase the priority of an item to the given value.
291 /// This function increases the priority of an item to the given value.
292 /// \param i The item.
293 /// \param p The priority.
294 /// \pre \e i must be stored in the heap with priority at most \e p.
295 void increase(const Item &i, const Prio &p) {
297 bubbleDown(idx, Pair(i,p), _data.size());
300 /// \brief Return the state of an item.
302 /// This method returns \c PRE_HEAP if the given item has never
303 /// been in the heap, \c IN_HEAP if it is in the heap at the moment,
304 /// and \c POST_HEAP otherwise.
305 /// In the latter case it is possible that the item will get back
306 /// to the heap again.
307 /// \param i The item.
308 State state(const Item &i) const {
314 /// \brief Set the state of an item in the heap.
316 /// This function sets the state of the given item in the heap.
317 /// It can be used to manually clear the heap when it is important
318 /// to achive better time complexity.
319 /// \param i The item.
320 /// \param st The state. It should not be \c IN_HEAP.
321 void state(const Item& i, State st) {
325 if (state(i) == IN_HEAP) erase(i);
333 /// \brief Replace an item in the heap.
335 /// This function replaces item \c i with item \c j.
336 /// Item \c i must be in the heap, while \c j must be out of the heap.
337 /// After calling this method, item \c i will be out of the
338 /// heap and \c j will be in the heap with the same prioriority
339 /// as item \c i had before.
340 void replace(const Item& i, const Item& j) {
342 _iim.set(i, _iim[j]);
344 _data[idx].first = j;
347 }; // class FouraryHeap
351 #endif // LEMON_FOURARY_HEAP_H