Welcome to our exploration of the stack data structure! A stack is a fundamental linear data structure that follows the Last-In, First-Out principle, also known as LIFO. Imagine a stack of plates in your kitchen - you can only add new plates to the top, and when you need a plate, you take the one from the top. This is exactly how a stack works in computer science.
Now let's explore the fundamental operations of a stack. The most important operations are Push and Pop. Push adds a new element to the top of the stack, while Pop removes the top element. We also have Peek or Top operation to view the top element without removing it, IsEmpty to check if the stack is empty, and Size to get the number of elements. The top of the stack is always where we perform these operations.
Let's see push and pop operations in action. We start with an empty stack, then push the value 5, followed by 10, and then 15. Notice how each new element goes to the top. Now for pop operations - when we pop, we get 15 first, then 10, leaving only 5 in the stack. This demonstrates the Last-In, First-Out principle perfectly.
Stacks can be implemented in two main ways. The array-based implementation uses a fixed-size array with a top pointer that tracks the current position. Push operation increments the top pointer and adds the value, while pop decrements the pointer and returns the value. The linked list implementation uses dynamic memory with nodes, where the head pointer represents the top of the stack. This approach allows for unlimited size but uses more memory per element.
Stacks are fundamental data structures with wide applications in computer science. They manage function calls in programming languages, evaluate mathematical expressions, enable undo and redo functionality in applications, support backtracking algorithms, and handle browser navigation history. The LIFO principle makes stacks perfect for scenarios where you need to reverse the order of operations or maintain a temporary storage that processes items in reverse order.