list.h

这是C＋＋编程经典的书上实例的源代码。 （英文名是《C＋＋ how to program》第3版）

// Fig. 15.3: list.h
// Template List class definition
#ifndef LIST_H
#define LIST_H

#include <iostream>
#include <cassert>
#include "listnd.h"

using std::cout;

template< class NODETYPE >
class List {
public:
   List();      // constructor
   ~List();     // destructor
   void insertAtFront( const NODETYPE & );
   void insertAtBack( const NODETYPE & );
   bool removeFromFront( NODETYPE & );
   bool removeFromBack( NODETYPE & );
   bool isEmpty() const;
   void print() const;
private:
   ListNode< NODETYPE > *firstPtr;  // pointer to first node
   ListNode< NODETYPE > *lastPtr;   // pointer to last node

   // Utility function to allocate a new node
   ListNode< NODETYPE > *getNewNode( const NODETYPE & );
};

// Default constructor
template< class NODETYPE >
List< NODETYPE >::List() : firstPtr( 0 ), lastPtr( 0 ) { }

// Destructor
template< class NODETYPE >
List< NODETYPE >::~List()
{
   if ( !isEmpty() ) {    // List is not empty
      cout << "Destroying nodes ...\n";

      ListNode< NODETYPE > *currentPtr = firstPtr, *tempPtr;

      while ( currentPtr != 0 ) {  // delete remaining nodes
         tempPtr = currentPtr;
         cout << tempPtr->data << '\n';
         currentPtr = currentPtr->nextPtr;
         delete tempPtr;
      }
   }

   cout << "All nodes destroyed\n\n";
}

// Insert a node at the front of the list
template< class NODETYPE >
void List< NODETYPE >::insertAtFront( const NODETYPE &value )
{
   ListNode< NODETYPE > *newPtr = getNewNode( value );

   if ( isEmpty() )  // List is empty
      firstPtr = lastPtr = newPtr;
   else {          // List is not empty
      newPtr->nextPtr = firstPtr;
      firstPtr = newPtr;
   }
}

// Insert a node at the back of the list
template< class NODETYPE >
void List< NODETYPE >::insertAtBack( const NODETYPE &value )
{
   ListNode< NODETYPE > *newPtr = getNewNode( value );

   if ( isEmpty() )  // List is empty
      firstPtr = lastPtr = newPtr;
   else {          // List is not empty
      lastPtr->nextPtr = newPtr;
      lastPtr = newPtr;
   }
}

// Delete a node from the front of the list
template< class NODETYPE >
bool List< NODETYPE >::removeFromFront( NODETYPE &value )
{
   if ( isEmpty() )             // List is empty
      return false;             // delete unsuccessful
   else {
      ListNode< NODETYPE > *tempPtr = firstPtr;

      if ( firstPtr == lastPtr )
         firstPtr = lastPtr = 0;
      else
         firstPtr = firstPtr->nextPtr;

      value = tempPtr->data;  // data being removed
      delete tempPtr;
      return true;            // delete successful
   }
}

// Delete a node from the back of the list
template< class NODETYPE >
bool List< NODETYPE >::removeFromBack( NODETYPE &value )
{
   if ( isEmpty() )
      return false;   // delete unsuccessful
   else {
      ListNode< NODETYPE > *tempPtr = lastPtr;

      if ( firstPtr == lastPtr )
         firstPtr = lastPtr = 0;
      else {
         ListNode< NODETYPE > *currentPtr = firstPtr;

         while ( currentPtr->nextPtr != lastPtr )
            currentPtr = currentPtr->nextPtr;

         lastPtr = currentPtr;
         currentPtr->nextPtr = 0;
      }

      value = tempPtr->data;
      delete tempPtr;
      return true;   // delete successful
   }
}

// Is the List empty?
template< class NODETYPE > 
bool List< NODETYPE >::isEmpty() const 
   { return firstPtr == 0; }

// Return a pointer to a newly allocated node
template< class NODETYPE >
ListNode< NODETYPE > *List< NODETYPE >::getNewNode( 
                                        const NODETYPE &value )
{
   ListNode< NODETYPE > *ptr = 
      new ListNode< NODETYPE >( value );
   assert( ptr != 0 );
   return ptr;
}

// Display the contents of the List
template< class NODETYPE >
void List< NODETYPE >::print() const
{
   if ( isEmpty() ) {
      cout << "The list is empty\n\n";
      return;
   }

   ListNode< NODETYPE > *currentPtr = firstPtr;

   cout << "The list is: ";

   while ( currentPtr != 0 ) {
      cout << currentPtr->data << ' ';
      currentPtr = currentPtr->nextPtr;
   }

   cout << "\n\n";
}

#endif


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