Difference between Stack and queue

This article includes stack and queue and difference between stack and queue. This is very important topic from interview point of view.

A data structure is a critical software component that helps store, retrieve and manage information. This information is often hierarchical in nature, meaning that it consists of multiple levels of data. A structure allows programmers to manage large amounts of complex information efficiently. Many different types of data structures exist, and each is designed to handle a particular class of data. Queues and stacks are two common data structures used in computer programming. Understanding how these structures work is crucial for writing effective software.In this article we will talk about Difference between Stack and queue.

Table of contents

• Difference between Stack and queue
• What is Stack?
• Application of Stack
• What is the queue?
• Application of Queue
• Key Points about Stack and Queue
• Conclusion

Difference between Stack and queue

Also explore: Data Structures and Algorithms Online Courses & Certifications

What is Stack?

A stack is a linear data structure that performs operations according to a specific order. For example, whenever you want to access an element in an array, you can, but for a stack data structure, there is only one sequence to access the element. In a stack, a push operation inserts elements from one end, and a pop operation removes elements from the same end. The end of the Stack used to perform all operations is called the top of the Stack. So the Stack follows the LIFO (Last In First Out) principle. The last inserted item is the first to be popped off the Stack. The most important thing to note about stack data structures is that they only contain elements of the same data type.

Example of Stack

• Some may eat cookies (or Poppins). Suppose you take out one cookie at a time by tearing only one side of the cover. This is called popping, and if you want to store the cookie for a while, put it back into the packet from the same torn end. This is called a push.
• Stack of books as shown in fig below.

Also read: Queue Data Structure: Types, Implementation, Applications

Application of Stack

• Stack is used for memory management.
• Used by the Java Virtual Machine.
• The Stack is used for expression conversion. For example, infix to postfix or prefix to postfix.
• Used for string parsing or string reversal.
• Stacks are used for matching HTML tags in web development.
• Used to solve the backtracking problem 
• The Stack is also used in function calls for recursive functions.

What is the queue?

A queue is a linear form of data structure. In this, Users can only insert items from one side of the list. They are known as back. You can also remove these elements from another face called the front face. This type of data structure follows the first-in-first-out (FIFO) principle. It means that the first item put on the list comes out first. The process of inserting items into a queue is called an enqueue operation. We refer to the process of removing an item as a dequeue operation. A user can always keep two pointers in a queue. The front pointer points to the first inserted item still in the list. The second pointer is the back pointer, which points to the last item inserted into the list.

Example of Queue

1. A restaurant may use queuing to manage its tables and chairs to serve all its customers efficiently.
2. Patients waiting for medical checkups or students waiting for their classes. 

Application of Queue

• Spooling on the printer
• Buffers for devices such as keyboards
• Applied to WhatsApp, if you send a message to a friend and you don’t have an internet connection, these messages will be queued on WhatsApp’s servers.
• It is used as a queue for a single shared resource such as CPU, disk, or printer.
• It is used as a buffer for MP3 players and portable CD players.
• It applies to the operating system to handle interrupts. 
• It applies to adding songs to the end or playing from the beginning.

Key Points about Stack and Queue

• The difference between a queue and a stack is that a stack is temporary, and a queue is permanent- unlike a stack, objects in a queue don’t move from one position to another.
• A queue is also more strict about how many items can be in one location. Objects in a queue must also move forward at a specific rate, or they’ll lose their place in line.
• Queues are usually more efficient than stacks because they move things along much faster.

Conclusion

Stacks and queues are two common data structures used in computer programming; understanding how these structures work is crucial for writing effective software. A queue consists of items added to the end and withdrawn from the top. Items enter a queue at the bottom and exit at the top. When an item leaves the top, another item can be added to it without interfering with the previous item. A stack consists of items added to the top and retrieved from the bottom.