Stacks and Queues: Use Cases

1. Use Cases for Stack (LIFO)

Use Case 1: Undo Feature in Text Editors

In a text editor, when you type something and want to "undo" an action, a stack is a great choice.

• Every time you make a change (like typing a letter or deleting), that action gets pushed onto a stack.
• When you hit "undo," the most recent action is popped off the stack and undone.
• The last change is always the first one undone, which is exactly how a stack works.

Example:

• You type "Hello" → push("Hello")
• You type "World" → push("World")
• You press "Undo" → pop() removes "World", so now you're back to "Hello".

Use Case 2: Browser History (Back Button)

When you browse websites, your browser keeps track of the pages you visited using a stack.

• Each time you visit a new page, it’s pushed onto the stack.
• When you press the "back" button, the most recent page is popped off, taking you back to the previous page.

Example:

• Visit Page1 → push("Page1")
• Visit Page2 → push("Page2")
• Click "Back" → pop() removes "Page2", you go back to "Page1".

---

2. Use Cases for Queue (FIFO)

Use Case 1: Print Queue

Imagine a printer that prints documents. The first document you send to the printer should be the first to print. A queue is perfect for this because of its FIFO (First In, First Out) nature.

• Documents are added to the end of the queue (enqueue).
• The printer processes and prints the document at the front of the queue (dequeue).

Example:

• Document1 → enqueue("Document1")
• Document2 → enqueue("Document2")
• Printer prints Document1 first → dequeue() removes "Document1".
• Now the printer prints Document2 → dequeue() removes "Document2".

Use Case 2: Customer Service Call Center

In a call center, customers are added to a queue when they call in. The first customer to call should be the first one to speak with an agent.

• As customers call in, they are added to the end of the queue.
• The agent picks the first person in the queue to speak with, then that person is removed from the queue.

Example:

• Customer1 calls → enqueue("Customer1")
• Customer2 calls → enqueue("Customer2")
• Agent answers Customer1 → dequeue() removes "Customer1".
• Next, the agent answers Customer2 → dequeue() removes "Customer2".

---

Why Use Stacks and Queues?

• Stacks help in scenarios where the most recent item is the one you want to access or remove first (e.g., undo actions, back button etc...).
• Queues are ideal when you want to process items in the order they were added, like in a line at a ticket counter or a printer queue.

These data structures are simple, but they efficiently manage tasks that require a specific order of processing!