Undo/Redo and Ticketing Line Systems

You've joined the internal tools team at a productivity software company. Two internal teams are requesting features for their systems: one team needs an Undo/Redo manager for a collaborative editor, and the other needs a Help Desk ticketing system to manage customer requests in the order they’re received.

Instead of relying on built-in lists or Python's deque, you're tasked with building two custom data structures, a Stack and a Queue, using nodes and pointers. Your program should run in the terminal and allow users to:

• Perform, undo, and redo actions using a custom stack
• Add customers, serve them in order, and monitor a help desk queue
• View the current state of each system interactively

This assignment builds your understanding of how stacks and queues behave under the hood, and how pointer-based logic differs from list-based operations. These skills are foundational for interview preparation and for building tools that require predictable control over the order in which data is accessed and processed.

File Structure

• node.py – Contains the shared Node class for both data structures
• undo_redo.py – Contains the Stack class and Undo/Redo CLI interface
• help_desk_queue.py – Contains the Queue class and Help Desk CLI interface

Classes

Node Class

Represents a single element in a linked structure.

Constructor

Node(value)

Attributes

• value (Any): The value stored in the node.
• next (Node or None): Pointer to the next node in the structure.

Stack Class

Implements a LIFO stack using linked nodes.

Constructor

Stack()

Attributes

• top (Node or None): Points to the top of the stack.

Methods

• push(value): Adds a value to the top of the stack.
• pop(): Removes and returns the top value.
• peek(): Returns the top value without removing it.
• print_stack(): Prints the stack from top to bottom.

Queue Class

Implements a FIFO queue using linked nodes.

Constructor

Queue()

Attributes

• front (Node or None): First item in the queue.
• rear (Node or None): Last item in the queue.

Methods

• enqueue(value): Adds a value to the end of the queue.
• dequeue(): Removes and returns the front value.
• peek(): Returns the front value without removing it.
• print_queue(): Prints the queue from front to rear.