Question

Write a program that creates a linked list object of 10 characters and creates a second list object containing a copy of the first list, but in reverse order.

Short answer

Create a Node and LinkedList class, insert 10 characters into the first linked list, implement a reversal method in the class, generate a reversed copy, and validate it.

Step-by-step solution

Define a Node class

The first step in creating a linked list is to define a Node class encapsulating the data and the pointer to the next node. Each node will store a character.

Define a LinkedList class

Create a LinkedList class to handle operations such as insertion at the end, which will be used to create the list, and a method to return a reversed copy.

Insert characters into the first list

Using the LinkedList class, insert 10 characters one by one at the end of the list to create the first linked list of characters.

Implement the reversal method

In the LinkedList class, implement a method to return a reversed copy of the linked list. This method should traverse the original list and create a new list by inserting each visited node at the beginning of the new list.

Create the reversed linked list

Call the reversal method on the first linked list to create a separate linked list which is the reversed copy of the first.

Test and validate

Write a simple routine to traverse each list and print out the characters. Verify the second list is indeed a reversed copy of the first.

Key concepts

Node class implementation

In C++, a linked list is a collection of nodes where each node is connected to the next one in the sequence. To implement a linked list, you first need to define a Node class. This class encapsulates two key elements: data and a pointer to the next node.

For our exercise, each node will store a single character. Here's a simplified structure of such a Node class in C++:
class Node {
public:
char data;
Node* next;
Node(char c) : data(c), next(nullptr) {}
};
This class has a constructor that initializes the node with a character and sets the 'next' pointer to null, indicating the end of the list. It's essential to get this foundational step right, as the rest of the linked list operations depend on a well-defined Node class.

By understanding the Node class, students will have an easier time grappling with more complex linked list operations.

LinkedList class operations

Once the Node class is implemented, the next step is to manage these nodes collectively through a LinkedList class. This class provides operations that allow you to work with the linked list as a whole, such as insertion, deletion, and traversal.

For our purpose, we'll focus on two operations: inserting characters at the end of the list and creating a reversed copy of the list. Here's how these operations are generally structured:

• Insertion at End: Loop through the list until you reach the last node, then set the 'next' pointer of the last node to the new node containing the inserted character.
• Creation of Reversed Copy: This involves traversing the original list and inserting each character into a new list such that each new node becomes the head of the list, effectively reversing the order of nodes.

This insertion and reversal are fundamental for list manipulations and can form the basis for more advanced operations like sorting or merging lists.

List reversal algorithm

Reversing a linked list is a common algorithmic problem that can showcase a student's understanding of linked list operations and pointer manipulation. The goal is to produce a new list in which the order of nodes is the inverse of the original list.

A simple algorithm for this operates in a linear manner. Starting with the head of the original list, you iterate through each node and insert it at the beginning of the new list. Here is a step-by-step concept of the algorithm:

• Initialize three pointers, namely 'current' which points to the head of the original list, 'prev' which is initialized to `nullptr`, and 'next' to temporarily hold the remaining list.
• Iterate through the list: For each node, first store the next node in 'next'. Then redirect the 'current' node's next pointer to 'prev', effectively changing the links. Move 'prev' to 'current', and 'current' to 'next', and proceed to the next node.
• Once all nodes are visited, 'prev' will be pointing to the new head of the reversed list.

By comprehending this list reversal algorithm, students will gain valuable insights into pointer manipulation and the iterative process of linked list traversal.