lemon/bin_heap.h
author Peter Kovacs <kpeter@inf.elte.hu>
Wed, 08 Jul 2009 17:47:01 +0200
changeset 758 28cfac049a6a
parent 757 f1fe0ddad6f7
child 1270 dceba191c00d
permissions -rw-r--r--
Unify member names in heaps (#299)

The following renamings are made.

Public members:
- UnderFlowPriorityError -> PriorityUnderflowError
("underflow" is only one word)

Private members:
- bubble_up() -> bubbleUp()
- bubble_down() -> bubbleDown()
- second_child() -> secondChild()
- makeroot() -> makeRoot()
- relocate_last() -> relocateLast()
- data -> _data
- boxes -> _boxes
     1 /* -*- mode: C++; indent-tabs-mode: nil; -*-
     2  *
     3  * This file is a part of LEMON, a generic C++ optimization library.
     4  *
     5  * Copyright (C) 2003-2009
     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 heaps
    23 ///\file
    24 ///\brief Binary heap implementation.
    25 
    26 #include <vector>
    27 #include <utility>
    28 #include <functional>
    29 
    30 namespace lemon {
    31 
    32   /// \ingroup heaps
    33   ///
    34   /// \brief Binary heap data structure.
    35   ///
    36   /// This class implements the \e binary \e heap data structure.
    37   /// It fully conforms to the \ref concepts::Heap "heap concept".
    38   ///
    39   /// \tparam PR Type of the priorities of the items.
    40   /// \tparam IM A read-writable item map with \c int values, used
    41   /// internally to handle the cross references.
    42   /// \tparam CMP A functor class for comparing the priorities.
    43   /// The default is \c std::less<PR>.
    44 #ifdef DOXYGEN
    45   template <typename PR, typename IM, typename CMP>
    46 #else
    47   template <typename PR, typename IM, typename CMP = std::less<PR> >
    48 #endif
    49   class BinHeap {
    50   public:
    51 
    52     /// Type of the item-int map.
    53     typedef IM ItemIntMap;
    54     /// Type of the priorities.
    55     typedef PR Prio;
    56     /// Type of the items stored in the heap.
    57     typedef typename ItemIntMap::Key Item;
    58     /// Type of the item-priority pairs.
    59     typedef std::pair<Item,Prio> Pair;
    60     /// Functor type for comparing the priorities.
    61     typedef CMP Compare;
    62 
    63     /// \brief Type to represent the states of the items.
    64     ///
    65     /// Each item has a state associated to it. It can 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 item-int map must be initialized in such way that it assigns
    70     /// \c PRE_HEAP (<tt>-1</tt>) to any element to be put in the heap.
    71     enum State {
    72       IN_HEAP = 0,    ///< = 0.
    73       PRE_HEAP = -1,  ///< = -1.
    74       POST_HEAP = -2  ///< = -2.
    75     };
    76 
    77   private:
    78     std::vector<Pair> _data;
    79     Compare _comp;
    80     ItemIntMap &_iim;
    81 
    82   public:
    83 
    84     /// \brief Constructor.
    85     ///
    86     /// Constructor.
    87     /// \param map A map that assigns \c int values to the items.
    88     /// It is used internally to handle the cross references.
    89     /// The assigned value must be \c PRE_HEAP (<tt>-1</tt>) for each item.
    90     explicit BinHeap(ItemIntMap &map) : _iim(map) {}
    91 
    92     /// \brief Constructor.
    93     ///
    94     /// Constructor.
    95     /// \param map A map that assigns \c int values to the items.
    96     /// It is used internally to handle the cross references.
    97     /// The assigned value must be \c PRE_HEAP (<tt>-1</tt>) for each item.
    98     /// \param comp The function object used for comparing the priorities.
    99     BinHeap(ItemIntMap &map, const Compare &comp)
   100       : _iim(map), _comp(comp) {}
   101 
   102 
   103     /// \brief The number of items stored in the heap.
   104     ///
   105     /// This function returns the number of items stored in the heap.
   106     int size() const { return _data.size(); }
   107 
   108     /// \brief Check if the heap is empty.
   109     ///
   110     /// This function returns \c true if the heap is empty.
   111     bool empty() const { return _data.empty(); }
   112 
   113     /// \brief Make the heap empty.
   114     ///
   115     /// This functon makes the heap empty.
   116     /// It does not change the cross reference map. If you want to reuse
   117     /// a heap that is not surely empty, you should first clear it and
   118     /// then you should set the cross reference map to \c PRE_HEAP
   119     /// for each item.
   120     void clear() {
   121       _data.clear();
   122     }
   123 
   124   private:
   125     static int parent(int i) { return (i-1)/2; }
   126 
   127     static int secondChild(int i) { return 2*i+2; }
   128     bool less(const Pair &p1, const Pair &p2) const {
   129       return _comp(p1.second, p2.second);
   130     }
   131 
   132     int bubbleUp(int hole, Pair p) {
   133       int par = parent(hole);
   134       while( hole>0 && less(p,_data[par]) ) {
   135         move(_data[par],hole);
   136         hole = par;
   137         par = parent(hole);
   138       }
   139       move(p, hole);
   140       return hole;
   141     }
   142 
   143     int bubbleDown(int hole, Pair p, int length) {
   144       int child = secondChild(hole);
   145       while(child < length) {
   146         if( less(_data[child-1], _data[child]) ) {
   147           --child;
   148         }
   149         if( !less(_data[child], p) )
   150           goto ok;
   151         move(_data[child], hole);
   152         hole = child;
   153         child = secondChild(hole);
   154       }
   155       child--;
   156       if( child<length && less(_data[child], p) ) {
   157         move(_data[child], hole);
   158         hole=child;
   159       }
   160     ok:
   161       move(p, hole);
   162       return hole;
   163     }
   164 
   165     void move(const Pair &p, int i) {
   166       _data[i] = p;
   167       _iim.set(p.first, i);
   168     }
   169 
   170   public:
   171 
   172     /// \brief Insert a pair of item and priority into the heap.
   173     ///
   174     /// This function inserts \c p.first to the heap with priority
   175     /// \c p.second.
   176     /// \param p The pair to insert.
   177     /// \pre \c p.first must not be stored in the heap.
   178     void push(const Pair &p) {
   179       int n = _data.size();
   180       _data.resize(n+1);
   181       bubbleUp(n, p);
   182     }
   183 
   184     /// \brief Insert an item into the heap with the given priority.
   185     ///
   186     /// This function inserts the given item into the heap with the
   187     /// given priority.
   188     /// \param i The item to insert.
   189     /// \param p The priority of the item.
   190     /// \pre \e i must not be stored in the heap.
   191     void push(const Item &i, const Prio &p) { push(Pair(i,p)); }
   192 
   193     /// \brief Return the item having minimum priority.
   194     ///
   195     /// This function returns the item having minimum priority.
   196     /// \pre The heap must be non-empty.
   197     Item top() const {
   198       return _data[0].first;
   199     }
   200 
   201     /// \brief The minimum priority.
   202     ///
   203     /// This function returns the minimum priority.
   204     /// \pre The heap must be non-empty.
   205     Prio prio() const {
   206       return _data[0].second;
   207     }
   208 
   209     /// \brief Remove the item having minimum priority.
   210     ///
   211     /// This function removes the item having minimum priority.
   212     /// \pre The heap must be non-empty.
   213     void pop() {
   214       int n = _data.size()-1;
   215       _iim.set(_data[0].first, POST_HEAP);
   216       if (n > 0) {
   217         bubbleDown(0, _data[n], n);
   218       }
   219       _data.pop_back();
   220     }
   221 
   222     /// \brief Remove the given item from the heap.
   223     ///
   224     /// This function removes the given item from the heap if it is
   225     /// already stored.
   226     /// \param i The item to delete.
   227     /// \pre \e i must be in the heap.
   228     void erase(const Item &i) {
   229       int h = _iim[i];
   230       int n = _data.size()-1;
   231       _iim.set(_data[h].first, POST_HEAP);
   232       if( h < n ) {
   233         if ( bubbleUp(h, _data[n]) == h) {
   234           bubbleDown(h, _data[n], n);
   235         }
   236       }
   237       _data.pop_back();
   238     }
   239 
   240     /// \brief The priority of the given item.
   241     ///
   242     /// This function returns the priority of the given item.
   243     /// \param i The item.
   244     /// \pre \e i must be in the heap.
   245     Prio operator[](const Item &i) const {
   246       int idx = _iim[i];
   247       return _data[idx].second;
   248     }
   249 
   250     /// \brief Set the priority of an item or insert it, if it is
   251     /// not stored in the heap.
   252     ///
   253     /// This method sets the priority of the given item if it is
   254     /// already stored in the heap. Otherwise it inserts the given
   255     /// item into the heap with the given priority.
   256     /// \param i The item.
   257     /// \param p The priority.
   258     void set(const Item &i, const Prio &p) {
   259       int idx = _iim[i];
   260       if( idx < 0 ) {
   261         push(i,p);
   262       }
   263       else if( _comp(p, _data[idx].second) ) {
   264         bubbleUp(idx, Pair(i,p));
   265       }
   266       else {
   267         bubbleDown(idx, Pair(i,p), _data.size());
   268       }
   269     }
   270 
   271     /// \brief Decrease the priority of an item to the given value.
   272     ///
   273     /// This function decreases the priority of an item to the given value.
   274     /// \param i The item.
   275     /// \param p The priority.
   276     /// \pre \e i must be stored in the heap with priority at least \e p.
   277     void decrease(const Item &i, const Prio &p) {
   278       int idx = _iim[i];
   279       bubbleUp(idx, Pair(i,p));
   280     }
   281 
   282     /// \brief Increase the priority of an item to the given value.
   283     ///
   284     /// This function increases the priority of an item to the given value.
   285     /// \param i The item.
   286     /// \param p The priority.
   287     /// \pre \e i must be stored in the heap with priority at most \e p.
   288     void increase(const Item &i, const Prio &p) {
   289       int idx = _iim[i];
   290       bubbleDown(idx, Pair(i,p), _data.size());
   291     }
   292 
   293     /// \brief Return the state of an item.
   294     ///
   295     /// This method returns \c PRE_HEAP if the given item has never
   296     /// been in the heap, \c IN_HEAP if it is in the heap at the moment,
   297     /// and \c POST_HEAP otherwise.
   298     /// In the latter case it is possible that the item will get back
   299     /// to the heap again.
   300     /// \param i The item.
   301     State state(const Item &i) const {
   302       int s = _iim[i];
   303       if( s>=0 )
   304         s=0;
   305       return State(s);
   306     }
   307 
   308     /// \brief Set the state of an item in the heap.
   309     ///
   310     /// This function sets the state of the given item in the heap.
   311     /// It can be used to manually clear the heap when it is important
   312     /// to achive better time complexity.
   313     /// \param i The item.
   314     /// \param st The state. It should not be \c IN_HEAP.
   315     void state(const Item& i, State st) {
   316       switch (st) {
   317       case POST_HEAP:
   318       case PRE_HEAP:
   319         if (state(i) == IN_HEAP) {
   320           erase(i);
   321         }
   322         _iim[i] = st;
   323         break;
   324       case IN_HEAP:
   325         break;
   326       }
   327     }
   328 
   329     /// \brief Replace an item in the heap.
   330     ///
   331     /// This function replaces item \c i with item \c j.
   332     /// Item \c i must be in the heap, while \c j must be out of the heap.
   333     /// After calling this method, item \c i will be out of the
   334     /// heap and \c j will be in the heap with the same prioriority
   335     /// as item \c i had before.
   336     void replace(const Item& i, const Item& j) {
   337       int idx = _iim[i];
   338       _iim.set(i, _iim[j]);
   339       _iim.set(j, idx);
   340       _data[idx].first = j;
   341     }
   342 
   343   }; // class BinHeap
   344 
   345 } // namespace lemon
   346 
   347 #endif // LEMON_BIN_HEAP_H