Difference between Stack and Queue Data Structures

Primarily, there are two types of data types − Primitive and Non-primitive.

• Primitive data types are predefined types of data, which are supported by the programming language.

• Non-primitive data types are not defined by the programming language, but are instead created by the programmer.

With this brief introduction to data types, let's start this article and differentiate Stack and Queue data structures.

Both Stack and Queue are types of data structures to store data in a particular order. A stack data structure is a type of linear list which allows the insertion or deletion of an element at one end only. A queue data structure is a linear list that allows the insertion of elements at one end and deletion of elements at another end.

Both Stack and Queue are types non-primitive data structures, but we can differentiate the two based on their internal implementation. Read this article to learn more about stack and queue data structures and how they are different from each other.

What is Stack Data Structure?

A Stack data structure is a type of linear list which allows the insertion and deletion of elements from one end only. Hence, the element that is inserted last will be removed first. For this reason, the stack data structure is also termed as Last In First Out (LIFO) list.

In a stack data structure, the term PUSH is used for the insertion operation, while the term POP is used for the delete operation. Another important point about the stack data structure is that it requires only one reference pointer. The most and least accessible elements of a stack are referred to as TOP and BOTTOM of the stack.

What is Queue Data Structure?

A Queue data structure is also a linear list, but it allows the insertion of elements at one end and deletion of elements at another end. Consequently, the elements of queue can be removed in the same order of the insertion. For this reason, the queue data structure is also known as First In First Out (FIFO) list.

In a queue data structure, the insertion operation is performed at the front end while the deletion operation is performed at the rear end. The term ENQUEUE is used to refer the insertion operation, whereas the term QUEUE is used to refer the deletion operation. Unlike a stack data structure, a queue data structure requires two reference pointers.

Difference between Stack and Queue

The following table highlights all the important differences between stack and queue −

Key

Stack

Queue

Internal Implementation

Stack is internally implemented in such a way that the element inserted at the last in stack would be the first element to come out of it. So, stack follows LIFO (Last in and First out).

A Queue is implemented in such manner that the element inserted at the first in queue would be the first element to come out of it. So queue follows FIFO (First in and First out).

Target element

In case of Stack operations on element take place only from one end of the list called the top.

In a Queue, insertion takes place at the rear of the list and the deletion takes place from the front of the list.

Label and Flag

In stacks, only one flag is maintained to access the list which always points to the last element present in the list.

In a queue, two flags are maintained to access the list. The front flag always points to the first element inserted in the list and is still present, and the rear flag always points to the last inserted element.

Operation

In a Stack, operations are termed as Push and Pop.

In a Queue, operations are termed as Enqueue and dequeue.

Implementation

Stack does not have any variant and thus do not implement further.

Queue has variants like circular queue, priority queue, doubly ended queue.

Complexity

As per above points the Stack is simpler than Queue.

Queue is more complex as compare to Stack.

Conclusion

The most significant difference that you should note here is that, in a stack, the elements can be accessed from one end only; whereas in a queue, the insertion operation takes place at the rear end of the list and the deletion operation takes place from the front of the list. A stack is a LIFO (Last In First Out) collection, while a queue is a FIFO (First In First Out) collection.

Updated on: 22-Feb-2023

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