Is Stack a LIFO or FIFO? [2024] 🔄

Have you ever wondered whether a stack follows the LIFO (Last In First Out) or FIFO (First In First Out) data structure type? It’s a common question that often arises when learning about data structures. In this article, we’ll dive deep into the topic and explore the characteristics of stacks and queues to understand their differences. So, let’s get started!

Table of Contents

• Quick Answer
• Quick Tips and Facts
• Background: Understanding Stacks and Queues
• Stack Data Structure: The LIFO Principle
• Queue Data Structure: The FIFO Principle
• Difference Between Stack and Queue
• Stack Variants and Queue Types
• Stack and Queue Visualization
• Stack and Queue Implementation
• FAQ
• Conclusion
• Recommended Links
• Reference Links

Quick Answer

• Stack follows the LIFO (Last In First Out) data structure type.
• Queue follows the FIFO (First In First Out) data structure type.

🔍 Quick Tips and Facts:

• Stacks and queues are linear forms of data structures.
• Stacks allow elements to be inserted and deleted from only one side (top).
• Queues allow elements to be inserted from the rear and deleted from the front.
• Stacks implement the LIFO principle, while queues implement the FIFO principle.

Background: Understanding Stacks and Queues

Before we delve into the differences between stacks and queues, let’s first understand what they are and how they work.

A stack is a linear data structure that follows the LIFO (Last In First Out) principle. It can be visualized as a vertical collection of elements, where the last element inserted is the first one to be removed. Think of it as a stack of books, where you can only remove the topmost book.

On the other hand, a queue is also a linear data structure, but it follows the FIFO (First In First Out) principle. It can be visualized as a horizontal collection of elements, where the first element inserted is the first one to be removed. Imagine a queue of people waiting in line, where the person who arrived first is the first one to leave.

Now that we have a basic understanding of stacks and queues, let’s explore their characteristics in more detail.

Stack Data Structure: The LIFO Principle

Stacks are known for their LIFO (Last In First Out) principle. This means that the last element inserted into the stack is the first one to be removed. Let’s take a closer look at the stack data structure:

Stack Rating:

Design: The design of a stack is simple and intuitive. It consists of a single pointer, known as the top, which points to the last element inserted. When a new element is added, the top pointer is incremented, and when an element is removed, the top pointer is decremented.

Functionality: Stacks are efficient for implementing algorithms that require a last-in-first-out order, such as function calls, expression evaluation, and backtracking. They provide operations like push (inserting an element) and pop (removing the top element).

Performance: Stacks have excellent performance characteristics. Both push and pop operations have a time complexity of O(1), meaning they take constant time regardless of the number of elements in the stack.

Cost-effectiveness: Stacks are cost-effective in terms of memory usage. They require a fixed amount of memory to store the elements, and the memory is allocated dynamically as elements are added or removed.

In summary, stacks are a reliable and efficient data structure for implementing LIFO behavior. They are widely used in various applications, including compilers, operating systems, and recursive algorithms.

Queue Data Structure: The FIFO Principle

Queues, on the other hand, follow the FIFO (First In First Out) principle. This means that the first element inserted into the queue is the first one to be removed. Let’s explore the characteristics of the queue data structure:

Queue Rating:

Design: A queue is designed with two pointers, known as the front and rear. The front pointer points to the first element in the queue, while the rear pointer points to the last element. New elements are inserted at the rear, and elements are removed from the front.

Functionality: Queues are ideal for scenarios that require a first-in-first-out order, such as scheduling processes, handling requests, and breadth-first search algorithms. They provide operations like enqueue (inserting an element) and dequeue (removing the front element).

Performance: The performance of queues is also excellent. Both enqueue and dequeue operations have a time complexity of O(1), making them efficient even for large queues.

Cost-effectiveness: Similar to stacks, queues are also cost-effective in terms of memory usage. They dynamically allocate memory as elements are added or removed, ensuring efficient memory utilization.

In summary, queues are a reliable and efficient data structure for implementing FIFO behavior. They find applications in various domains, including operating systems, network protocols, and simulations.

Difference Between Stack and Queue

Now that we have explored the characteristics of stacks and queues individually, let’s compare them to understand their differences. Here are the key points of distinction:

1. Basics:

   • Stack: Objects are removed or inserted at the same end (top).
   • Queue: Objects are removed and inserted from two different ends (front and rear).

2. Working Principle:

   • Stack: Follows the LIFO (Last In First Out) principle.
   • Queue: Follows the FIFO (First In First Out) principle.

3. Pointers:

   • Stack: Uses one pointer (top) to keep track of the last element.
   • Queue: Uses two pointers (front and rear) to keep track of the first and last elements.

4. Operations:

   • Stack: Provides push (inserting an element) and pop (removing the top element) operations.
   • Queue: Provides enqueue (inserting an element) and dequeue (removing the front element) operations.

5. Structure:

   • Stack: Insertion and deletion happen at one end (top).
   • Queue: Uses both front and rear ends for insertion and deletion.

6. Full Condition Examination:

   • Stack: The stack is considered full when the top pointer reaches the maximum capacity (top == max-1).
   • Queue: The queue is considered full when the rear pointer reaches the maximum capacity (rear == max-1).

7. Empty Condition Examination:

   • Stack: The stack is considered empty when the top pointer is -1 (top == -1).
   • Queue: The queue is considered empty when the front pointer is equal to the rear pointer plus one (front = rear+1) or when the front pointer is -1 (front == -1).

8. Variants:

   • Stack: Stacks do not have any specific types.
   • Queue: Queues have three types – circular queue, priority queue, and double-ended queue.

🔍 FAQ

Is an array LIFO or FIFO?

An array can be used to implement both LIFO (stack) and FIFO (queue) data structures. It depends on how the array is accessed and manipulated.

Which data structure uses LIFO?

The stack data structure uses the LIFO (Last In First Out) principle. It is designed to allow elements to be inserted and removed from the same end (top).

What is the difference between LIFO and Filo?

LIFO and Filo are two different acronyms for the same concept: Last In First Out. Both terms refer to the principle followed by the stack data structure.

Which data structure uses FIFO?

The queue data structure uses the FIFO (First In First Out) principle. It is designed to allow elements to be inserted at one end (rear) and removed from the other end (front).

Can a stack be empty and full at the same time?

No, a stack cannot be empty and full at the same time. If the stack is empty, it means there are no elements in it. If the stack is full, it means it has reached its maximum capacity.

Can a queue be empty and full at the same time?

No, a queue cannot be empty and full at the same time. If the queue is empty, it means there are no elements in it. If the queue is full, it means it has reached its maximum capacity.

Can a stack and a queue have the same elements?

Yes, a stack and a queue can have the same elements. However, the order in which the elements are accessed and removed will be different due to the LIFO and FIFO principles followed by stacks and queues, respectively.

Conclusion

In conclusion, a stack follows the LIFO (Last In First Out) data structure type, while a queue follows the FIFO (First In First Out) data structure type. Stacks and queues are both linear data structures but differ in their working principles and operations. Stacks are efficient for implementing algorithms that require a last-in-first-out order, while queues are ideal for scenarios that require a first-in-first-out order.

Whether you need to implement a stack or a queue depends on the specific requirements of your application. Consider the characteristics and advantages of each data structure to make an informed decision.

We hope this article has provided you with a comprehensive understanding of the differences between stacks and queues. If you have any further questions, feel free to explore the recommended links below or check out our other articles on game development, programming languages, Java development, software architecture, and JavaScript frameworks.

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Reference Links

• Difference Between Stack and Queue Data Structures – BYJU’S