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/* C++ Programming, Example answer, Exercise 2a, Sheet 8  */

/* Author: Rob Miller and William Knottenbelt
   Program last changed: 30th September 2001    */

/* This program creates a linked list of strings, and prints it out 
both forwards and backwards. */ 

#include <iostream>
#include <cstdlib>
#include <cstring>
using namespace std;

const int MAX_WORD_LENGTH = 80;

/* definition of a node */
struct Node;
typedef Node *Node_ptr;

struct Node
{
	char word[MAX_WORD_LENGTH];
	Node_ptr ptr_to_next_node;
};

/* Function to assign a linked list to "a_node" */
void assign_list(Node_ptr &a_list);

/* Function to assign a new dynamic node variable to "a_node" */
void assign_new_node(Node_ptr &a_node);

/* Function to print the strings in the list "a_node" forwards */
void print_list_forwards(Node_ptr a_node);

/* Function to print the strings in the list "a_node" backwards*/
void print_list_backwards(Node_ptr a_node);

/* MAIN PROGRAM */
int main()
{
	Node_ptr my_list = NULL;

	assign_list(my_list);

	cout << "
THE LIST FORWARDS IS:
";
	print_list_forwards(my_list);

	cout << "

THE LIST BACKWARDS IS:
";
	print_list_backwards(my_list);
	cout << "
";
			
	return 0;
}
/* END OF MAIN PROGRAM */
	
/* DEFINITION OF FUNCTION "assign_list" */
void assign_list(Node_ptr &a_list)
{
	Node_ptr current_node, last_node;
	
	assign_new_node(a_list);
	cout << "Enter first word (or '.' to end list): ";
	cin >> a_list->word;
	if (!strcmp(".",a_list->word))
	{
		delete a_list;
		a_list = NULL;
	}
	current_node = a_list;
	
	while (current_node != NULL)
	{
		assign_new_node(last_node);
		cout << "Enter next word (or '.' to end list): ";
		cin >> last_node->word;
		if (!strcmp(".",last_node->word))
		{
			delete last_node;
			last_node = NULL;
		}
		current_node->ptr_to_next_node = last_node;
		current_node = last_node;
	}
}	
/* END OF FUNCTION DEFINITION */

/* DEFINITION OF FUNCTION "assign_new_node" */
void assign_new_node(Node_ptr &a_node)
{
	a_node = new node;
	if (a_node == NULL) 
	{
		cout << "sorry - no more memory
"; 
		exit(1);
	}
}
/* END OF FUNCTION DEFINITION */

Cho mình hỏi chỗ void assign_new_node(Node_ptr &a_node)
Node_ptr là con trỏ mà truyền thêm & nó có ý nghĩa gì trong hàm đó.