C++ Programming Code Examples
C++ > Data Structures and Algorithm Analysis in C++ Code Examples
Header file for linked list
/* Header file for linked list */
#ifndef LinkedList_H
#define LinkedList_H
#include "dsexceptions.h"
#include <iostream.h> // For NULL
// List class
//
// CONSTRUCTION: with no initializer
// Access is via ListItr class
//
// **************PUBLIC OPERATIONS****************
// boolean isEmpty( ) --> Return true if empty; else false
// void makeEmpty( ) --> Remove all items
// ListItr zeroth( ) --> Return position to prior to first
// ListItr first( ) --> Return first position
// void insert( x, p ) --> Insert x after current iterator position p
// void remove( x ) --> Remove x
// ListItr find( x ) --> Return position that views x
// ListItr findPrevious( x )
// --> Return position prior to x
// **************ERRORS***************************
// No special errors
template <class Object>
class List; // Incomplete declaration.
template <class Object>
class ListItr; // Incomplete declaration.
template <class Object>
class ListNode
{
ListNode( const Object & theElement = Object( ), ListNode * n = NULL )
: element( theElement ), next( n ) { }
Object element;
ListNode *next;
friend class List<Object>;
friend class ListItr<Object>;
};
template <class Object>
class List
{
public:
List( );
List( const List & rhs );
~List( );
bool isEmpty( ) const;
void makeEmpty( );
ListItr<Object> zeroth( ) const;
ListItr<Object> first( ) const;
void insert( const Object & x, const ListItr<Object> & p );
ListItr<Object> find( const Object & x ) const;
ListItr<Object> findPrevious( const Object & x ) const;
void remove( const Object & x );
const List & operator=( const List & rhs );
private:
ListNode<Object> *header;
};
// ListItr class; maintains "current position"
//
// CONSTRUCTION: Package friendly only, with a ListNode
//
// **************PUBLIC OPERATIONS*****************
// bool isPastEnd( ) --> True if past end position in list
// void advance( ) --> Advance (if not already null)
// Object retrieve --> Return item in current position
template <class Object>
class ListItr
{
public:
ListItr( ) : current( NULL ) { }
bool isPastEnd( ) const
{ return current == NULL; }
void advance( )
{ if( !isPastEnd( ) ) current = current->next; }
const Object & retrieve( ) const
{ if( isPastEnd( ) ) throw BadIterator( );
return current->element; }
private:
ListNode<Object> *current; // Current position
ListItr( ListNode<Object> *theNode )
: current( theNode ) { }
friend class List<Object>; // Grant access to constructor
};
#include "LinkedList.cpp"
#endif
A friend function of a class is defined outside that class' scope but it has the right to access all private and protected members of the class. Even though the prototypes for friend functions appear in the class definition, friends are not member functions. A friend can be a function, function template, or member function, or a class or class template, in which case the entire class and all of its members are friends. If a function is defined as a friend function in C++ programming language, then the protected and private data of a class can be accessed using the function. By using the keyword friend compiler knows the given function is a friend function. For accessing the data, the declaration of a friend function should be done inside the body of a class starting with the keyword friend.
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