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PairingHeap.h

/**
 * \brief Pairing heap datastructure implementation
 *
 * Based on example code in "Data structures and Algorithm Analysis in C++"
 * by Mark Allen Weiss, used and released under the LGPL by permission
 * of the author.
 *
 * No promises about correctness.  Use at your own risk!
 *
 * Authors:
 *   Mark Allen Weiss
 *   Tim Dwyer <tgdwyer@gmail.com>
 *
 * Copyright (C) 2005 Authors
 *
 * Released under GNU LGPL.  Read the file 'COPYING' for more information.
 */
#ifndef PAIRING_HEAP_H_
#define PAIRING_HEAP_H_
#include <stdlib.h>
#include <fstream>
// Pairing heap class
//
// CONSTRUCTION: with no parameters
//
// ******************PUBLIC OPERATIONS*********************
// PairNode & insert( x ) --> Insert x
// deleteMin( minItem )   --> Remove (and optionally return) smallest item
// T findMin( )  --> Return smallest item
// bool isEmpty( )        --> Return true if empty; else false
// bool isFull( )         --> Return true if empty; else false
// void makeEmpty( )      --> Remove all items
// void decreaseKey( PairNode p, newVal )
//                        --> Decrease value in node p
// ******************ERRORS********************************
// Throws Underflow as warranted


// Node and forward declaration because g++ does
// not understand nested classes.
template <class T> 
class PairingHeap;

template <class T>
std::ostream& operator<< (std::ostream &os,const PairingHeap<T> &b);

template <class T>
class PairNode
{
      friend std::ostream& operator<< <T>(std::ostream &os,const PairingHeap<T> &b);
      T   element;
      PairNode    *leftChild;
      PairNode    *nextSibling;
      PairNode    *prev;

      PairNode( const T & theElement ) :
                  element( theElement ),
            leftChild(NULL), nextSibling(NULL), prev(NULL)
            { }
      friend class PairingHeap<T>;
};

template <class T>
class Comparator
{
public:
      virtual bool isLessThan(T const &lhs, T const &rhs) const = 0;
};

template <class T>
class PairingHeap
{
      friend std::ostream& operator<< <T>(std::ostream &os,const PairingHeap<T> &b);
public:
      PairingHeap( bool (*lessThan)(T const &lhs, T const &rhs) );
      PairingHeap( const PairingHeap & rhs );
      ~PairingHeap( );

      bool isEmpty( ) const;
      bool isFull( ) const;
      int size();

      PairNode<T> *insert( const T & x );
      const T & findMin( ) const;
      void deleteMin( );
      const T extractMin( ) {
            T v = findMin();
            deleteMin();
            return v;
      }
      void makeEmpty( );
      void decreaseKey( PairNode<T> *p, const T & newVal );
      void merge( PairingHeap<T> *rhs )
      {     
            PairNode<T> *broot=rhs->getRoot();
            if (root == NULL) {
                  if(broot != NULL) {
                        root = broot;
                  }
            } else {
                  compareAndLink(root, broot);
            }
            counter+=rhs->size();
      }

      const PairingHeap & operator=( const PairingHeap & rhs );
protected:
      PairNode<T> * getRoot() {
            PairNode<T> *r=root;
            root=NULL;
            return r;
      }
private:
      PairNode<T> *root;
      bool (*lessThan)(T const &lhs, T const &rhs);
      int counter;
      void reclaimMemory( PairNode<T> *t ) const;
      void compareAndLink( PairNode<T> * & first, PairNode<T> *second ) const;
      PairNode<T> * combineSiblings( PairNode<T> *firstSibling ) const;
      PairNode<T> * clone( PairNode<T> * t ) const;
};

#include "PairingHeap.cpp"
#endif

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