This repository contains the implementation of fundamental data structures in Python: Node, Stack, Queue, and DoublyLinkedList. They were made from scraps of my labs in the university. Feel free to use them however you like.

The Node class is the building block for linked data structures. Each node contains:

• value: The data stored in the node.
• next: A reference to the next Node in the sequence.
• prev: A reference to the previous Node (used in doubly linked lists).

The Stack class represents a stack data structure with Last In, First Out (LIFO) behavior, with the following operations:

• is_empty(): Check if the stack is empty.
• push(): Add a new Node with the provided value to the top of the stack.
• pop(): Remove and return the value from the top of the stack.
• peek(): Return the value from the top without removing it.
• size(): Return the number of items in the stack.

The Queue class represents a queue data structure with First In, First Out (FIFO) behavior, with the following operations:

• is_empty(): Check if the queue is empty.
• enqueue(): Add a new Node with the provided value to the end of the queue.
• dequeue(): Remove and return the value from the front of the queue.
• size(): Return the number of items in the queue.

The DoublyLinkedList class represents a doubly linked list, allowing insertion and deletion of nodes from both ends efficiently, with the following operations:

• is_empty(): Check if the list is empty.
• append(): Add a new Node with the provided value to the end of the list.
• insertBefore(): Insert a Node before a given node in the list.
• insertAfter(): Insert a Node after a given node in the list.
• remove(): Remove the first Node with the provided value from the list.
• remove_node(): Remove the specified Node from the list.
• __str__: Return a string representation of the list's values.

The data structures are implemented to provide basic functionality and serve as a foundation for more complex algorithms and applications.