lemon-0.x: lemon/bin_heap.h@d7442141d9ef

     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  */

    19 #ifndef LEMON_BIN_HEAP_H

    20 #define LEMON_BIN_HEAP_H

    22 ///\ingroup auxdat

    23 ///\file

    24 ///\brief Binary Heap implementation.

    26 #include <vector>

    27 #include <utility>

    28 #include <functional>

    30 namespace lemon {

    32   /// \ingroup auxdat

    34   /// A Binary Heap implementation.

    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 {

    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;

    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     };

    77   private:

    78     std::vector<PairType> data;

    79     Compare comp;

    80     ItemIntMap &iim;

    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) {}

    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) {}

   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(); }

   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(); }

   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     }

   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     }

   130     int bubble_up(int hole, PairType p);

   131     int bubble_down(int hole, PairType p, int length);

   133     void move(const PairType &p, int i) {

   134       data[i] = p;

   135       iim.set(p.first, i);

   136     }

   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     }

   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     }

   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)); }

   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     }

   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     }

   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     }

   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     }

   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     }

   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     }

   233     /// \brief Decreases the priority of \c i to \c p.

   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     }

   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     }

   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     }

   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     }

   293   }; // class BinHeap

   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   }

   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   }

   332 } // namespace lemon

   334 #endif // LEMON_BIN_HEAP_H

author	deba
	Wed, 01 Mar 2006 10:25:30 +0000
changeset 1991	d7442141d9ef
parent 1906	7fa90b66ca9e
child 2050	d9a221218ea4
permissions	-rw-r--r--