Welcome! In this lesson, we'll expand on our linked list implementation using Ruby. As you know by now, linked lists in Ruby require the manual creation and management of nodes and pointers. You'll learn how to build and improve on linked lists by defining your own classes and methods, providing an efficient way to perform data operations.

In Ruby, a doubly-linked list can be constructed manually by defining a Node class, where each node points to the next and previous nodes, facilitating bidirectional traversal. This structure allows flexible data management but requires careful handling of node connections to avoid complexity and errors.

To construct a linked list in Ruby, we define our own Node and LinkedList classes to manage the nodes and their connections:

In this code, we've set up a LinkedList with a head that starts as nil. Next, we'll add methods for connecting nodes and managing this list.

Here are some custom methods we can define in Ruby to manipulate our linked list:

• add_last(value): Appends an element to the end of the list.
• add_first(value): Inserts an element at the beginning of the list.
• remove_first: Removes the first element of the list.
• find(value): Searches for the first occurrence of the specified value.

An example implementation might look like this:

To traverse a linked list in Ruby, you can use a loop to manually follow each node's connections:

We can implement more complex linked list operations in Ruby, such as:

• add_after(node, value): Inserts a new node after the specified existing node.
• add_before(node, value): Inserts a new node before the specified existing node.
• clear: Removes all elements from the list.
• contains(value): Checks if the list contains the specified element.

Here's how these methods would look:

Congratulations! You've learned how to create and manipulate linked lists from scratch in Ruby. We covered implementing nodes, managing connections, and performing operations such as adding, removing, and traversing elements. Now, practice creating your own linked list implementations and building functionality to reinforce your understanding and prepare for more complex data structure challenges in Ruby. Happy coding!