vmap.h: Enables one to create maps with a virtual base class.
3 * This file is a part of LEMON, a generic C++ optimization library
5 * Copyright (C) 2003-2006
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_RADIX_HEAP_H
20 #define LEMON_RADIX_HEAP_H
24 ///\brief Radix Heap implementation.
27 #include <lemon/error.h>
31 /// \brief Exception thrown by RadixHeap.
33 /// This Exception is thrown when a smaller priority
34 /// is inserted into the \e RadixHeap then the last time erased.
36 /// \author Balazs Dezso
38 class UnderFlowPriorityError : public RuntimeError {
40 virtual const char* exceptionName() const {
41 return "lemon::UnderFlowPriorityError";
47 /// \brief A Radix Heap implementation.
49 /// This class implements the \e radix \e heap data structure. A \e heap
50 /// is a data structure for storing items with specified values called \e
51 /// priorities in such a way that finding the item with minimum priority is
52 /// efficient. This heap type can store only items with \e int priority.
53 /// In a heap one can change the priority of an item, add or erase an
54 /// item, but the priority cannot be decreased under the last removed
57 /// \param _Item Type of the items to be stored.
58 /// \param _ItemIntMap A read and writable Item int map, used internally
59 /// to handle the cross references.
63 /// \author Balazs Dezso
65 template <typename _Item, typename _ItemIntMap>
71 typedef _ItemIntMap ItemIntMap;
73 /// \brief Type to represent the items states.
75 /// Each Item element have a state associated to it. It may be "in heap",
76 /// "pre heap" or "post heap". The latter two are indifferent from the
77 /// heap's point of view, but may be useful to the user.
79 /// The ItemIntMap \e should be initialized in such way that it maps
80 /// PRE_HEAP (-1) to any element to be put in the heap...
93 RadixItem(Item _item, int _prio) : item(_item), prio(_prio) {}
99 RadixBox(int _min, int _size) : first(-1), min(_min), size(_size) {}
102 std::vector<RadixItem> data;
103 std::vector<RadixBox> boxes;
109 /// \brief The constructor.
113 /// \param _iim It should be given to the constructor, since it is used
114 /// internally to handle the cross references. The value of the map
115 /// should be PRE_HEAP (-1) for each element.
117 /// \param minimal The initial minimal value of the heap.
118 /// \param capacity It determines the initial capacity of the heap.
119 RadixHeap(ItemIntMap &_iim, int minimal = 0, int capacity = 0)
121 boxes.push_back(RadixBox(minimal, 1));
122 boxes.push_back(RadixBox(minimal + 1, 1));
123 while (lower(boxes.size() - 1, capacity + minimal - 1)) {
128 /// The number of items stored in the heap.
130 /// \brief Returns the number of items stored in the heap.
131 int size() const { return data.size(); }
132 /// \brief Checks if the heap stores no items.
134 /// Returns \c true if and only if the heap stores no items.
135 bool empty() const { return data.empty(); }
137 /// \brief Make empty this heap.
139 /// Make empty this heap.
140 void clear(int minimal = 0, int capacity = 0) {
141 for (int i = 0; i < (int)data.size(); ++i) {
142 iim[data[i].item] = -2;
144 data.clear(); boxes.clear();
145 boxes.push_back(RadixBox(minimal, 1));
146 boxes.push_back(RadixBox(minimal + 1, 1));
147 while (lower(boxes.size() - 1, capacity + minimal - 1)) {
154 bool upper(int box, Prio prio) {
155 return prio < boxes[box].min;
158 bool lower(int box, Prio prio) {
159 return prio >= boxes[box].min + boxes[box].size;
162 /// \brief Remove item from the box list.
163 void remove(int index) {
164 if (data[index].prev >= 0) {
165 data[data[index].prev].next = data[index].next;
167 boxes[data[index].box].first = data[index].next;
169 if (data[index].next >= 0) {
170 data[data[index].next].prev = data[index].prev;
174 /// \brief Insert item into the box list.
175 void insert(int box, int index) {
176 if (boxes[box].first == -1) {
177 boxes[box].first = index;
178 data[index].next = data[index].prev = -1;
180 data[index].next = boxes[box].first;
181 data[boxes[box].first].prev = index;
182 data[index].prev = -1;
183 boxes[box].first = index;
185 data[index].box = box;
188 /// \brief Add a new box to the box list.
190 int min = boxes.back().min + boxes.back().size;
191 int size = 2 * boxes.back().size;
192 boxes.push_back(RadixBox(min, size));
195 /// \brief Move an item up into the proper box.
196 void bubble_up(int index) {
197 if (!lower(data[index].box, data[index].prio)) return;
199 int box = findUp(data[index].box, data[index].prio);
203 /// \brief Find up the proper box for the item with the given prio.
204 int findUp(int start, int prio) {
205 while (lower(start, prio)) {
206 if (++start == (int)boxes.size()) {
213 /// \brief Move an item down into the proper box.
214 void bubble_down(int index) {
215 if (!upper(data[index].box, data[index].prio)) return;
217 int box = findDown(data[index].box, data[index].prio);
221 /// \brief Find up the proper box for the item with the given prio.
222 int findDown(int start, int prio) {
223 while (upper(start, prio)) {
224 if (--start < 0) throw UnderFlowPriorityError();
229 /// \brief Find the first not empty box.
232 while (boxes[first].first == -1) ++first;
236 /// \brief Gives back the minimal prio of the box.
237 int minValue(int box) {
238 int min = data[boxes[box].first].prio;
239 for (int k = boxes[box].first; k != -1; k = data[k].next) {
240 if (data[k].prio < min) min = data[k].prio;
245 /// \brief Rearrange the items of the heap and makes the
246 /// first box not empty.
248 int box = findFirst();
249 if (box == 0) return;
250 int min = minValue(box);
251 for (int i = 0; i <= box; ++i) {
253 min += boxes[i].size;
255 int curr = boxes[box].first, next;
257 next = data[curr].next;
263 void relocate_last(int index) {
264 if (index != (int)data.size() - 1) {
265 data[index] = data.back();
266 if (data[index].prev != -1) {
267 data[data[index].prev].next = index;
269 boxes[data[index].box].first = index;
271 if (data[index].next != -1) {
272 data[data[index].next].prev = index;
274 iim[data[index].item] = index;
281 /// \brief Insert an item into the heap with the given priority.
283 /// Adds \c i to the heap with priority \c p.
284 /// \param i The item to insert.
285 /// \param p The priority of the item.
286 void push(const Item &i, const Prio &p) {
289 data.push_back(RadixItem(i, p));
290 while (lower(boxes.size() - 1, p)) {
293 int box = findDown(boxes.size() - 1, p);
297 /// \brief Returns the item with minimum priority.
299 /// This method returns the item with minimum priority.
300 /// \pre The heap must be nonempty.
302 const_cast<RadixHeap<Item, ItemIntMap>&>(*this).moveDown();
303 return data[boxes[0].first].item;
306 /// \brief Returns the minimum priority.
308 /// It returns the minimum priority.
309 /// \pre The heap must be nonempty.
311 const_cast<RadixHeap<Item, ItemIntMap>&>(*this).moveDown();
312 return data[boxes[0].first].prio;
315 /// \brief Deletes the item with minimum priority.
317 /// This method deletes the item with minimum priority.
318 /// \pre The heap must be non-empty.
321 int index = boxes[0].first;
322 iim[data[index].item] = POST_HEAP;
324 relocate_last(index);
327 /// \brief Deletes \c i from the heap.
329 /// This method deletes item \c i from the heap, if \c i was
330 /// already stored in the heap.
331 /// \param i The item to erase.
332 void erase(const Item &i) {
336 relocate_last(index);
339 /// \brief Returns the priority of \c i.
341 /// This function returns the priority of item \c i.
342 /// \pre \c i must be in the heap.
343 /// \param i The item.
344 Prio operator[](const Item &i) const {
346 return data[idx].prio;
349 /// \brief \c i gets to the heap with priority \c p independently
350 /// if \c i was already there.
352 /// This method calls \ref push(\c i, \c p) if \c i is not stored
353 /// in the heap and sets the priority of \c i to \c p otherwise.
354 /// It may throw an \e UnderFlowPriorityException.
355 /// \param i The item.
356 /// \param p The priority.
357 void set(const Item &i, const Prio &p) {
362 else if( p >= data[idx].prio ) {
372 /// \brief Decreases the priority of \c i to \c p.
374 /// This method decreases the priority of item \c i to \c p.
375 /// \pre \c i must be stored in the heap with priority at least \c p, and
376 /// \c should be greater or equal to the last removed item's priority.
377 /// \param i The item.
378 /// \param p The priority.
379 void decrease(const Item &i, const Prio &p) {
385 /// \brief Increases the priority of \c i to \c p.
387 /// This method sets the priority of item \c i to \c p.
388 /// \pre \c i must be stored in the heap with priority at most \c p
389 /// \param i The item.
390 /// \param p The priority.
391 void increase(const Item &i, const Prio &p) {
397 /// \brief Returns if \c item is in, has already been in, or has
398 /// never been in the heap.
400 /// This method returns PRE_HEAP if \c item has never been in the
401 /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP
402 /// otherwise. In the latter case it is possible that \c item will
403 /// get back to the heap again.
404 /// \param i The item.
405 state_enum state(const Item &i) const {
408 return state_enum(s);
411 /// \brief Sets the state of the \c item in the heap.
413 /// Sets the state of the \c item in the heap. It can be used to
414 /// manually clear the heap when it is important to achive the
415 /// better time complexity.
416 /// \param i The item.
417 /// \param st The state. It should not be \c IN_HEAP.
418 void state(const Item& i, state_enum st) {
422 if (state(i) == IN_HEAP) {
432 }; // class RadixHeap
436 #endif // LEMON_RADIX_HEAP_H