# What Is Stack and Queue Data Structure?

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Larry Thompson

What Is Stack and Queue Data Structure?

A data structure is a way of organizing and storing data in a computer’s memory so that it can be accessed and manipulated efficiently. Two commonly used data structures are stacks and queues.

In this article, we will explore what these data structures are, how they work, and their applications in programming.

## Stack Data Structure

A stack is a collection of elements that follows the Last-In-First-Out (LIFO) principle. It means that the element inserted last is the first one to be removed. Imagine stacking books on top of each otherâ€”a new book is always placed on top, and when you want to remove a book, you take it from the top.

In programming, a stack can be thought of as a linear structure with two main operations: push (insertion) and pop (removal). The push operation adds an element to the top of the stack, while the pop operation removes the topmost element.

To represent a stack in code, we can use an array or linked list. Each time an element is pushed or popped from the stack, its size changes accordingly.

### Applications of Stacks:

• Evaluation of expressions: Stacks are commonly used to evaluate arithmetic expressions by converting them into postfix or prefix form.
• Balancing parentheses: Stacks help in checking whether parentheses in an expression are balanced or not.
• Backtracking: Many algorithms involve backtracking where stacks are used to store states.

## Queue Data Structure

A queue is a collection of elements that follows the First-In-First-Out (FIFO) principle. It means that the element inserted first is the first one to be removed. Think of a queue at a ticket counterâ€”the person who arrives first gets their ticket first.

In programming, a queue can be visualized as a linear structure with two main operations: enqueue (insertion) and dequeue (removal). The enqueue operation adds an element to the rear end of the queue, while the dequeue operation removes an element from the front end.

To implement a queue, we can use an array or linked list. Just like stacks, the size of the queue changes as elements are enqueued or dequeued.

### Applications of Queues:

• Job scheduling: Queues are used in operating systems for scheduling processes and tasks.
• Breadth-first search: Queues play a crucial role in graph algorithms like breadth-first search.
• Buffering: In computer networks, queues are used for buffering packets before transmitting them.

In conclusion, both stacks and queues are fundamental data structures that have various applications in programming. Understanding their principles and implementations can greatly enhance your problem-solving abilities. So go ahead, experiment with these data structures, and unlock new possibilities in your code!