Hello, dear student! Today's lesson will take you on an exciting journey through Stacks, a fundamental data structure widely used in programming with various applications. Our goal for this lesson is to understand the concept of stacks, learn how to apply and manipulate them in Ruby, and delve deeply into their complexities. Let’s get started!

First and foremost, let's understand what a Stack is. Imagine a stack of plates that you can only remove from the top. That’s exactly what a Stack is: a Last-In, First-Out (LIFO) structure. Stacks are used in memory management, backtracking algorithms, and more. The key operations involved are Push (adding an element to the top of the stack), Pop (removing the topmost element), and Peek (looking at the topmost element without removing it).

In Ruby, stacks can be easily implemented using the built-in Array class. The array acts as a dynamic structure that can efficiently handle the required stack operations. Let’s look into creating a stack using an array in Ruby:

In this example, stack is our empty array ready to be used as a stack.

A Stack involves three primary operations: Push, Pop, and Peek. In Ruby's Array, the push operation adds a new element to the end of the array, which serves as the top of the stack. Here's how we can perform a push operation:

This code sequence adds the elements 10, 20, and 30 to the stack, with 30 being the topmost element.

The Pop operation removes the topmost element from the Stack, which is the last element of the array in Ruby:

Here, stack.pop removes 30 from the stack and returns it, allowing you to access the element that was removed.

Lastly, the Peek operation returns the topmost element without removing it from the Stack. In Ruby, we can access the last element using the last method:

This operation checks the top element without altering the stack, which remains unchanged.

Congratulations, you've completed the lesson on Stacks in Ruby! You will now proceed to the practice session using the concepts learned here. These hands-on exercises will help solidify your knowledge and enhance your problem-solving skills. So, roll up your sleeves and dive right in!