What is a Stack?

A stack is a data structure that follows Last-In-First-Out (LIFO) — like a stack of plates. You add plates to the top and take them from the top. The last plate you put on is the first one you take off.

Operations:

• Push: Add an item to the top
• Pop: Remove and return the top item
• Peek/Top: Look at the top item without removing it
• IsEmpty: Check if the stack is empty

Why It's Useful:

• Function calls: Programming languages use stacks to track function calls
• Undo operations: Stacks remember what you did
• Expression evaluation: Parsing mathematical expressions
• Backtracking: Solving problems by trying and undoing

Real-World Analogy:

Think of a browser's back button. Each page you visit gets "pushed" onto a stack. When you hit back, it "pops" the most recent page.