lemon/concepts/heap.h
author Balazs Dezso <deba@inf.elte.hu>
Thu, 04 Mar 2010 10:17:02 +0100
changeset 871 86613aa28a0c
parent 709 0747f332c478
child 817 b87f0504cdbe
permissions -rw-r--r--
Fix documentation issues (#314)
     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_CONCEPTS_HEAP_H
    20 #define LEMON_CONCEPTS_HEAP_H
    21 
    22 ///\ingroup concept
    23 ///\file
    24 ///\brief The concept of heaps.
    25 
    26 #include <lemon/core.h>
    27 #include <lemon/concept_check.h>
    28 
    29 namespace lemon {
    30 
    31   namespace concepts {
    32 
    33     /// \addtogroup concept
    34     /// @{
    35 
    36     /// \brief The heap concept.
    37     ///
    38     /// This concept class describes the main interface of heaps.
    39     /// The various \ref heaps "heap structures" are efficient
    40     /// implementations of the abstract data type \e priority \e queue.
    41     /// They store items with specified values called \e priorities
    42     /// in such a way that finding and removing the item with minimum
    43     /// priority are efficient. The basic operations are adding and
    44     /// erasing items, changing the priority of an item, etc.
    45     ///
    46     /// Heaps are crucial in several algorithms, such as Dijkstra and Prim.
    47     /// Any class that conforms to this concept can be used easily in such
    48     /// algorithms.
    49     ///
    50     /// \tparam PR Type of the priorities of the items.
    51     /// \tparam IM A read-writable item map with \c int values, used
    52     /// internally to handle the cross references.
    53     /// \tparam CMP A functor class for comparing the priorities.
    54     /// The default is \c std::less<PR>.
    55 #ifdef DOXYGEN
    56     template <typename PR, typename IM, typename CMP>
    57 #else
    58     template <typename PR, typename IM, typename CMP = std::less<PR> >
    59 #endif
    60     class Heap {
    61     public:
    62 
    63       /// Type of the item-int map.
    64       typedef IM ItemIntMap;
    65       /// Type of the priorities.
    66       typedef PR Prio;
    67       /// Type of the items stored in the heap.
    68       typedef typename ItemIntMap::Key Item;
    69 
    70       /// \brief Type to represent the states of the items.
    71       ///
    72       /// Each item has a state associated to it. It can be "in heap",
    73       /// "pre-heap" or "post-heap". The latter two are indifferent from the
    74       /// heap's point of view, but may be useful to the user.
    75       ///
    76       /// The item-int map must be initialized in such way that it assigns
    77       /// \c PRE_HEAP (<tt>-1</tt>) to any element to be put in the heap.
    78       enum State {
    79         IN_HEAP = 0,    ///< = 0. The "in heap" state constant.
    80         PRE_HEAP = -1,  ///< = -1. The "pre-heap" state constant.
    81         POST_HEAP = -2  ///< = -2. The "post-heap" state constant.
    82       };
    83 
    84       /// \brief Constructor.
    85       ///
    86       /// Constructor.
    87       /// \param map A map that assigns \c int values to keys of type
    88       /// \c Item. It is used internally by the heap implementations to
    89       /// handle the cross references. The assigned value must be
    90       /// \c PRE_HEAP (<tt>-1</tt>) for each item.
    91       explicit Heap(ItemIntMap &map) {}
    92 
    93       /// \brief Constructor.
    94       ///
    95       /// Constructor.
    96       /// \param map A map that assigns \c int values to keys of type
    97       /// \c Item. It is used internally by the heap implementations to
    98       /// handle the cross references. The assigned value must be
    99       /// \c PRE_HEAP (<tt>-1</tt>) for each item.
   100       /// \param comp The function object used for comparing the priorities.
   101       explicit Heap(ItemIntMap &map, const CMP &comp) {}
   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 0; }
   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 false; }
   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 
   122       /// \brief Insert an item into the heap with the given priority.
   123       ///
   124       /// This function inserts the given item into the heap with the
   125       /// given priority.
   126       /// \param i The item to insert.
   127       /// \param p The priority of the item.
   128       /// \pre \e i must not be stored in the heap.
   129       void push(const Item &i, const Prio &p) {}
   130 
   131       /// \brief Return the item having minimum priority.
   132       ///
   133       /// This function returns the item having minimum priority.
   134       /// \pre The heap must be non-empty.
   135       Item top() const {}
   136 
   137       /// \brief The minimum priority.
   138       ///
   139       /// This function returns the minimum priority.
   140       /// \pre The heap must be non-empty.
   141       Prio prio() const {}
   142 
   143       /// \brief Remove the item having minimum priority.
   144       ///
   145       /// This function removes the item having minimum priority.
   146       /// \pre The heap must be non-empty.
   147       void pop() {}
   148 
   149       /// \brief Remove the given item from the heap.
   150       ///
   151       /// This function removes the given item from the heap if it is
   152       /// already stored.
   153       /// \param i The item to delete.
   154       /// \pre \e i must be in the heap.
   155       void erase(const Item &i) {}
   156 
   157       /// \brief The priority of the given item.
   158       ///
   159       /// This function returns the priority of the given item.
   160       /// \param i The item.
   161       /// \pre \e i must be in the heap.
   162       Prio operator[](const Item &i) const {}
   163 
   164       /// \brief Set the priority of an item or insert it, if it is
   165       /// not stored in the heap.
   166       ///
   167       /// This method sets the priority of the given item if it is
   168       /// already stored in the heap. Otherwise it inserts the given
   169       /// item into the heap with the given priority.
   170       ///
   171       /// \param i The item.
   172       /// \param p The priority.
   173       void set(const Item &i, const Prio &p) {}
   174 
   175       /// \brief Decrease the priority of an item to the given value.
   176       ///
   177       /// This function decreases the priority of an item to the given value.
   178       /// \param i The item.
   179       /// \param p The priority.
   180       /// \pre \e i must be stored in the heap with priority at least \e p.
   181       void decrease(const Item &i, const Prio &p) {}
   182 
   183       /// \brief Increase the priority of an item to the given value.
   184       ///
   185       /// This function increases the priority of an item to the given value.
   186       /// \param i The item.
   187       /// \param p The priority.
   188       /// \pre \e i must be stored in the heap with priority at most \e p.
   189       void increase(const Item &i, const Prio &p) {}
   190 
   191       /// \brief Return the state of an item.
   192       ///
   193       /// This method returns \c PRE_HEAP if the given item has never
   194       /// been in the heap, \c IN_HEAP if it is in the heap at the moment,
   195       /// and \c POST_HEAP otherwise.
   196       /// In the latter case it is possible that the item will get back
   197       /// to the heap again.
   198       /// \param i The item.
   199       State state(const Item &i) const {}
   200 
   201       /// \brief Set the state of an item in the heap.
   202       ///
   203       /// This function sets the state of the given item in the heap.
   204       /// It can be used to manually clear the heap when it is important
   205       /// to achive better time complexity.
   206       /// \param i The item.
   207       /// \param st The state. It should not be \c IN_HEAP.
   208       void state(const Item& i, State st) {}
   209 
   210 
   211       template <typename _Heap>
   212       struct Constraints {
   213       public:
   214         void constraints() {
   215           typedef typename _Heap::Item OwnItem;
   216           typedef typename _Heap::Prio OwnPrio;
   217           typedef typename _Heap::State OwnState;
   218 
   219           Item item;
   220           Prio prio;
   221           item=Item();
   222           prio=Prio();
   223           ignore_unused_variable_warning(item);
   224           ignore_unused_variable_warning(prio);
   225 
   226           OwnItem own_item;
   227           OwnPrio own_prio;
   228           OwnState own_state;
   229           own_item=Item();
   230           own_prio=Prio();
   231           ignore_unused_variable_warning(own_item);
   232           ignore_unused_variable_warning(own_prio);
   233           ignore_unused_variable_warning(own_state);
   234 
   235           _Heap heap1(map);
   236           _Heap heap2 = heap1;
   237           ignore_unused_variable_warning(heap1);
   238           ignore_unused_variable_warning(heap2);
   239 
   240           int s = heap.size();
   241           ignore_unused_variable_warning(s);
   242           bool e = heap.empty();
   243           ignore_unused_variable_warning(e);
   244 
   245           prio = heap.prio();
   246           item = heap.top();
   247           prio = heap[item];
   248           own_prio = heap.prio();
   249           own_item = heap.top();
   250           own_prio = heap[own_item];
   251 
   252           heap.push(item, prio);
   253           heap.push(own_item, own_prio);
   254           heap.pop();
   255 
   256           heap.set(item, prio);
   257           heap.decrease(item, prio);
   258           heap.increase(item, prio);
   259           heap.set(own_item, own_prio);
   260           heap.decrease(own_item, own_prio);
   261           heap.increase(own_item, own_prio);
   262 
   263           heap.erase(item);
   264           heap.erase(own_item);
   265           heap.clear();
   266 
   267           own_state = heap.state(own_item);
   268           heap.state(own_item, own_state);
   269 
   270           own_state = _Heap::PRE_HEAP;
   271           own_state = _Heap::IN_HEAP;
   272           own_state = _Heap::POST_HEAP;
   273         }
   274 
   275         _Heap& heap;
   276         ItemIntMap& map;
   277       };
   278     };
   279 
   280     /// @}
   281   } // namespace lemon
   282 }
   283 #endif