DSA Lecture 2: The Secret Behind Undo, Redo & Browser History (Stacks)

Have you ever wondered how your browser's Back button works, or how Undo and Redo work in applications ? The answer is often a powerful data structure called a Stack . Designed for IT and Software Engineering students, beginners, and those preparing for interviews, this video breaks down everything you need to know about stacks . We cover the theory behind Abstract Data Types (ADTs), how to write the code in Java, and how to use stacks to optimize real-world algorithms like the Stock Span problem . In this video, you will learn: What Abstract Data Types (ADTs) are The Last-In-First-Out (LIFO) principle and core stack operations (Push, Pop, Top, Size, isEmpty) How to build an Array-based Stack implementation using Java Interfaces and Exceptions How to optimize the famous Stock Span Problem from a slow O(n 2 ) to a lightning-fast linear O(n) time complexity How Growable Stacks work and the fundamentals of Amortized Analysis Video Chapters: Introduction to Stacks: What is an Abstract Data Type (ADT) and the Last-In-First-Out (LIFO) principle . Core Operations: Understanding push(), pop(), top(), size(), and isEmpty() . Java Interfaces & Exceptions: Bridging theory and code. Separating specification from implementation and handling edge cases with StackEmptyException . The Array Implementation: Building an ArrayStack and achieving constant O(1) time complexity for basic operations . Real-World Application (Stock Span Problem): Using a stack for time series analysis to optimize a brute-force O(n 2 ) algorithm down to linear O(n) time . Growable Stacks & Amortized Analysis: What happens when the array gets full? Comparing the inefficient "tight strategy" against the highly efficient "growth strategy" (array doubling) . If you found this video helpful, don't forget to Like, Share, and Subscribe! Happy Coding! 🚀 #java #datastructures #stacks #softwareengineering #codinginterviews #learntocode #algorithms