Chapter 6 - Stacks and Queues

Introduction

In the world of data structures, stacks and queues are foundational concepts that enable efficient data management and manipulation. Understanding these structures is crucial for solving a multitude of programming problems, from parsing expressions to managing sequential tasks.

• Stacks follow a "Last In, First Out" (LIFO) approach, meaning the last element added is the first to be removed.
• Queues use a "First In, First Out" (FIFO) approach, where the first element added is the first to be removed.

In this chapter, we'll dive into the definitions, operations, implementation, and real-world applications of stacks and queues in C++. Let's unleash our inner hacker as we explore these essential data structures!

Stacks

Definition and Operations

A stack is a linear data structure that allows operations primarily at one end. Here are the primary operations associated with stacks:

• Push: Add an element to the top of the stack.
• Pop: Remove the top element from the stack.
• Peek/Top: View the top element without removing it.
• IsEmpty: Check if the stack is empty.

Implementing a Stack Using Arrays

Let's implement a stack using an array in C++:

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Implementing a Stack Using Linked Lists

We can also implement a stack using a linked list:

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Queues

Definition and Operations

A queue is a linear data structure that follows FIFO behavior. The key operations are:

• Enqueue: Add an element to the back of the queue.
• Dequeue: Remove the front element from the queue.
• Front: View the front element without removing it.
• IsEmpty: Check if the queue is empty.

Implementing a Queue Using Arrays

Here's a basic implementation using an array:

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Implementing a Queue Using Linked Lists

Now, let's implement a queue using a linked list:

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Real-World Applications of Stacks and Queues

• Stacks:

  • Undo mechanisms in text editors (last action undone first).
  • Function call management in programming languages (keeping track of active functions).
  • Expression evaluation and parsing (in compilers).

• Queues:

  • Task scheduling (maintaining the order of tasks to be processed).
  • Buffer management (like IO Buffers or print spooling).
  • Handling requests in a web server (FIFO for processing requests).

Practical Exercises

1. Stack Exercises:

   • Implement a function to check if a string has balanced parentheses using a stack.
   • Create a program that converts a decimal number to binary using a stack.

2. Queue Exercises:

   • Implement a queue using a circular array and handle the wrap-around condition.
   • Write a program that simulates a simple checkout line using a queue (enqueue customers, dequeue them after processing).

Chapter Summary

In this chapter, we explored:

• The definitions and operational mechanisms of stacks and queues.
• The implementation of these data structures using arrays and linked lists.
• Real-world use cases for stacks and queues.

Understanding stacks and queues enhances your problem-solving toolkit, allowing you to approach challenges with structured methodologies. Keep experimenting with the code, and gear up for more advanced data structures and algorithms in the next chapters!