alpar@906: /* -*- C++ -*-
alpar@921:  * src/lemon/bin_heap.h - Part of LEMON, a generic C++ optimization library
klao@39:  *
alpar@1164:  * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
alpar@906:  * (Egervary Combinatorial Optimization Research Group, EGRES).
klao@39:  *
alpar@906:  * Permission to use, modify and distribute this software is granted
alpar@906:  * provided that this copyright notice appears in all copies. For
alpar@906:  * precise terms see the accompanying LICENSE file.
klao@39:  *
alpar@906:  * This software is provided "AS IS" with no warranty of any kind,
alpar@906:  * express or implied, and with no claim as to its suitability for any
alpar@906:  * purpose.
klao@39:  *
klao@39:  */
klao@39: 
alpar@921: #ifndef LEMON_BIN_HEAP_H
alpar@921: #define LEMON_BIN_HEAP_H
klao@37: 
klao@491: ///\ingroup auxdat
klao@274: ///\file
klao@274: ///\brief Binary Heap implementation.
klao@274: 
klao@37: #include <vector>
klao@37: #include <utility>
klao@37: #include <functional>
klao@37: 
alpar@921: namespace lemon {
klao@37: 
alpar@430:   /// \addtogroup auxdat
alpar@430:   /// @{
alpar@430: 
jacint@1270:   /// A Binary Heap implementation.
alpar@967:   
jacint@1270:   ///This class implements the \e binary \e heap data structure. A \e heap
jacint@1270:   ///is a data structure for storing items with specified values called \e
jacint@1270:   ///priorities in such a way that finding the item with minimum priority is
jacint@1270:   ///efficient. \c Compare specifies the ordering of the priorities. In a heap
jacint@1270:   ///one can change the priority of an item, add or erase an item, etc.
jacint@1270:   ///
jacint@1270:   ///\param Item Type of the items to be stored.  
jacint@1270:   ///\param Prio Type of the priority of the items.
jacint@1270:   ///\param ItemIntMap A read and writable Item int map, used internally
jacint@1270:   ///to handle the cross references.
jacint@1270:   ///\param Compare A class for the ordering of the priorities. The
jacint@1270:   ///default is \c std::less<Prio>.
alpar@967:   ///
alpar@967:   ///\sa FibHeap
alpar@967:   ///\sa Dijkstra
klao@172:   template <typename Item, typename Prio, typename ItemIntMap,
klao@172: 	    typename Compare = std::less<Prio> >
klao@37:   class BinHeap {
klao@37: 
klao@37:   public:
klao@172:     typedef Item                             ItemType;
klao@37:     // FIXME: stl-ben nem ezt hivjak value_type -nak, hanem a kovetkezot...
klao@172:     typedef Prio                             PrioType;
klao@172:     typedef std::pair<ItemType,PrioType>     PairType;
klao@172:     typedef ItemIntMap                       ItemIntMapType;
klao@172:     typedef Compare                          PrioCompare;
klao@37: 
klao@37:     /**
klao@172:      * Each Item element have a state associated to it. It may be "in heap",
klao@37:      * "pre heap" or "post heap". The later two are indifferent from the
klao@37:      * heap's point of view, but may be useful to the user.
klao@37:      *
klao@172:      * The ItemIntMap _should_ be initialized in such way, that it maps
klao@37:      * PRE_HEAP (-1) to any element to be put in the heap...
klao@37:      */
klao@274:     ///\todo it is used nowhere
klao@274:     ///
klao@39:     enum state_enum {
klao@37:       IN_HEAP = 0,
klao@37:       PRE_HEAP = -1,
klao@37:       POST_HEAP = -2
klao@37:     };
klao@37: 
klao@37:   private:
klao@37:     std::vector<PairType> data;
klao@37:     Compare comp;
klao@37:     // FIXME: jo ez igy???
klao@172:     ItemIntMap &iim;
klao@37: 
klao@37:   public:
jacint@1270:     ///The constructor
jacint@1270: 
jacint@1270:     /**
jacint@1270:        \c _iim should be given to the constructor, since it is used
jacint@1270:        internally to handle the cross references.
jacint@1270:     */
deba@1185:     explicit BinHeap(ItemIntMap &_iim) : iim(_iim) {}
jacint@1270:     
jacint@1270:     ///The constructor
jacint@1270: 
jacint@1270:     /**
jacint@1270:        \c _iim should be given to the constructor, since it is used
jacint@1270:        internally to handle the cross references. \c _comp is an
jacint@1270:        object for ordering of the priorities.
jacint@1270:     */
deba@1191:     BinHeap(ItemIntMap &_iim, const Compare &_comp) 
deba@1185:       : iim(_iim), comp(_comp) {}
klao@37: 
klao@37: 
jacint@1270:     ///The number of items stored in the heap.
jacint@1270: 
jacint@1270:     /**
jacint@1270:        Returns the number of items stored in the heap.
jacint@1270:     */
klao@37:     int size() const { return data.size(); }
jacint@1270:     
jacint@1270:     ///Checks if the heap stores no items.
jacint@1270:     
jacint@1270:     /**
jacint@1270:        Returns \c true if and only if the heap stores no items.
jacint@1270:     */
klao@41:     bool empty() const { return data.empty(); }
klao@37: 
klao@37:   private:
klao@37:     static int parent(int i) { return (i-1)/2; }
klao@37:     static int second_child(int i) { return 2*i+2; }
klao@214:     bool less(const PairType &p1, const PairType &p2) const {
klao@37:       return comp(p1.second, p2.second);
klao@37:     }
klao@37: 
klao@37:     int bubble_up(int hole, PairType p);
klao@37:     int bubble_down(int hole, PairType p, int length);
klao@37: 
klao@37:     void move(const PairType &p, int i) {
klao@37:       data[i] = p;
klao@172:       iim.set(p.first, i);
klao@37:     }
klao@37: 
klao@41:     void rmidx(int h) {
klao@41:       int n = data.size()-1;
klao@41:       if( h>=0 && h<=n ) {
klao@172: 	iim.set(data[h].first, POST_HEAP);
klao@41: 	if ( h<n ) {
klao@41: 	  bubble_down(h, data[n], n);
klao@41: 	}
klao@41: 	data.pop_back();
klao@41:       }
klao@41:     }
klao@41: 
klao@37:   public:
jacint@1270:     ///Adds \c p.first to the heap with priority \c p.second.
jacint@1270:     
jacint@1270:     /**
jacint@1270:        Adds \c p.first to the heap with priority \c p.second.
jacint@1270:        \c p.first must not be stored in the heap. 
jacint@1270:     */
klao@37:     void push(const PairType &p) {
klao@37:       int n = data.size();
klao@37:       data.resize(n+1);
klao@37:       bubble_up(n, p);
klao@37:     }
jacint@1270: 
jacint@1270:     ///Adds \c i to the heap with priority \c p. 
jacint@1270:     
jacint@1270:     /**
jacint@1270:        Adds \c i to the heap with priority \c p. 
jacint@1270:        \pre \c i must not be stored in the heap. 
jacint@1270:     */
klao@172:     void push(const Item &i, const Prio &p) { push(PairType(i,p)); }
klao@37: 
jacint@1270:     ///Returns the item with minimum priority relative to \c Compare.
jacint@1270:     
jacint@1270:     /**
jacint@1270:        This method returns the item with minimum priority relative to \c
jacint@1270:        Compare.  
jacint@1270:        \pre The heap must be nonempty.  
jacint@1270:     */
klao@172:     Item top() const {
klao@37:       return data[0].first;
klao@37:     }
jacint@1270: 
jacint@1270:     ///Returns the minimum priority relative to \c Compare.
jacint@1270: 
jacint@1270:     /**
jacint@1270:        It returns the minimum priority relative to \c Compare.
jacint@1270:        \pre The heap must be nonempty.
jacint@1270:     */
klao@274:     Prio prio() const {
klao@37:       return data[0].second;
klao@37:     }
klao@37: 
jacint@1270:     ///Deletes the item with minimum priority relative to \c Compare.
jacint@1270: 
jacint@1270:     /**
jacint@1270:     This method deletes the item with minimum priority relative to \c
jacint@1270:     Compare from the heap.  
jacint@1270:     \pre The heap must be non-empty.  
jacint@1270:     */
klao@37:     void pop() {
klao@41:       rmidx(0);
klao@41:     }
klao@41: 
jacint@1270:     ///Deletes \c i from the heap.
jacint@1270: 
jacint@1270:     /**
jacint@1270:        This method deletes item \c i from the heap, if \c i was
jacint@1270:        already stored in the heap. 
jacint@1270:     */
klao@172:     void erase(const Item &i) {
jacint@221:       rmidx(iim[i]);
klao@37:     }
klao@37: 
jacint@1270:     
jacint@1270:     ///Returns the priority of \c i.
jacint@1270: 
jacint@1270:     /**
jacint@1270:        This function returns the priority of item \c i.  
jacint@1270:        \pre \c i must be in the heap.
jacint@1270:     */
klao@274:     Prio operator[](const Item &i) const {
jacint@221:       int idx = iim[i];
klao@37:       return data[idx].second;
klao@37:     }
klao@274: 
jacint@1270:     ///\c i gets to the heap with priority \c p independently if \c i was already there.
jacint@1270: 
jacint@1270:     /**
jacint@1270:        This method calls \ref push(\c i, \c p) if \c i is not stored
jacint@1270:        in the heap and sets the priority of \c i to \c p otherwise.
jacint@1270:     */
klao@172:     void set(const Item &i, const Prio &p) {
jacint@221:       int idx = iim[i];
klao@37:       if( idx < 0 ) {
klao@172: 	push(i,p);
klao@37:       }
klao@172:       else if( comp(p, data[idx].second) ) {
klao@172: 	bubble_up(idx, PairType(i,p));
klao@37:       }
klao@37:       else {
klao@172: 	bubble_down(idx, PairType(i,p), data.size());
klao@37:       }
klao@37:     }
klao@37: 
jacint@1270:     ///Decreases the priority of \c i to \c p.
jacint@1270: 
jacint@1270:     /**
jacint@1270:        This method decreases the priority of item \c i to \c p.
jacint@1270:        \pre \c i must be stored in the heap with priority at least \c
jacint@1270:        p relative to \c Compare.
jacint@1270:     */
klao@172:     void decrease(const Item &i, const Prio &p) {
jacint@221:       int idx = iim[i];
klao@172:       bubble_up(idx, PairType(i,p));
klao@37:     }
jacint@1270:     
jacint@1270:     ///Increases the priority of \c i to \c p.
jacint@1270: 
jacint@1270:     /**
jacint@1270:        This method sets the priority of item \c i to \c p. 
jacint@1270:        \pre \c i must be stored in the heap with priority at most \c
jacint@1270:        p relative to \c Compare.
jacint@1270:     */
klao@172:     void increase(const Item &i, const Prio &p) {
jacint@221:       int idx = iim[i];
klao@172:       bubble_down(idx, PairType(i,p), data.size());
klao@37:     }
klao@37: 
jacint@1270:     ///Returns if \c item is in, has already been in, or has never been in the heap.
jacint@1270: 
jacint@1270:     /**
jacint@1270:        This method returns PRE_HEAP if \c item has never been in the
jacint@1270:        heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP
jacint@1270:        otherwise. In the latter case it is possible that \c item will
jacint@1270:        get back to the heap again.
jacint@1270:     */
klao@172:     state_enum state(const Item &i) const {
jacint@221:       int s = iim[i];
klao@39:       if( s>=0 )
klao@39: 	s=0;
klao@39:       return state_enum(s);
klao@39:     }
klao@39: 
klao@37:   }; // class BinHeap
klao@37: 
klao@37:   
klao@37:   template <typename K, typename V, typename M, typename C>
klao@37:   int BinHeap<K,V,M,C>::bubble_up(int hole, PairType p) {
klao@37:     int par = parent(hole);
klao@37:     while( hole>0 && less(p,data[par]) ) {
klao@37:       move(data[par],hole);
klao@37:       hole = par;
klao@37:       par = parent(hole);
klao@37:     }
klao@37:     move(p, hole);
klao@37:     return hole;
klao@37:   }
klao@37: 
klao@37:   template <typename K, typename V, typename M, typename C>
klao@37:   int BinHeap<K,V,M,C>::bubble_down(int hole, PairType p, int length) {
klao@37:     int child = second_child(hole);
klao@37:     while(child < length) {
klao@37:       if( less(data[child-1], data[child]) ) {
klao@37: 	--child;
klao@37:       }
klao@37:       if( !less(data[child], p) )
klao@37: 	goto ok;
klao@37:       move(data[child], hole);
klao@37:       hole = child;
klao@37:       child = second_child(hole);
klao@37:     }
klao@37:     child--;
klao@37:     if( child<length && less(data[child], p) ) {
klao@37:       move(data[child], hole);
klao@37:       hole=child;
klao@37:     }
klao@37:   ok:
klao@37:     move(p, hole);
klao@37:     return hole;
klao@37:   }
klao@37: 
alpar@430:   ///@}
alpar@430: 
alpar@921: } // namespace lemon
klao@37: 
alpar@921: #endif // LEMON_BIN_HEAP_H