Advantages, Disadvantages And Uses Of a Doubly Linked List

Introduction

With such large amounts of data, it becomes imperative to derive efficient ways to organize it so that we save time and memory. Mastering these concepts will give a boost to your preparation for interviews in which data structure is one of the most important topics. A linked list is one such important data structure. 

We know that a linked list is a linear data structure that does not store the elements at contiguous memory locations. Rather, they are stored at random locations connected through pointers. 

There are three types of linked lists:

In this article, we will explore the advantages, disadvantages as well as uses of doubly-linked listsFirst, let’s see what a doubly-linked list is and how it differs from a singly linked list? Check out our video to get a detailed insight into doubly-linked lists. 

Doubly Linked List

In a singly-linked list, each node contains two pieces of information: data and a pointer to the next node. But in the doubly linked list, each node contains an extra piece of information called the previous pointer. The previous pointer points to the previous node corresponding to each node in the linked list.

To learn the concepts of doubly-linked lists in detail here's an amazing article: Introduction and Implementation of Doubly Linked Lists.

Advantages of Doubly Linked List

  • It allows traversing in both forward and backward directions because of the next and previous pointers, unlike the singly linked list, which allows traversing in only one direction.
     
  • Deletion of nodes is easier compared to a singly linked list. This is because to delete a node; we need access to the node to be deleted and the node previous to it. So, in a singly linked list, for deletion, we require two pointers, while in a doubly-linked list, there is no need to maintain an extra pointer as each node itself carries the information of the previous node.
     
  • Reversing a doubly linked list is also easy. We only need to swap each node’s next and previous pointers and update the head node to point to the last node to reverse a doubly-linked list. 
     
  • We can easily insert a  new node before a given node.

Disadvantages of Doubly Linked List

  • It consumes extra memory space compared to a singly linked list due to the extra previous pointer it has to maintain for each node.
    Note: This disadvantage can be overcome using XOR linked lists.
     
  • It is impossible to access the list’s elements randomly because they are stored at random locations, and we can only access them sequentially.
     
  • All the operations require more time due to the overhead of handling extra pointers. For instance, if you have to insert a new node, you also need to modify the previous pointers and the next pointers, similarly in the case of deletion.

Uses of Doubly Linked List

In this section, we will see some of the practical applications of the doubly linked list.

  • It is used in web browsers to implement the backward and forward navigation of web pages through the back and forward buttons.
     
  • Various applications implement the Undo and Redo functionality using a doubly-linked list.
     
  • Doubly linked lists are used in constructing the Most recently used(MRU) or Least Recently Used(LRU) cache.
     
  • It is used in games. For example, to represent the classical deck of cards.
     
  • Various data structures can be implemented like stacks, hash-tables, binary trees etc.
     
  • The thread scheduler uses them in the operating system to maintain a list of all the running processes.

FAQs

What are the different types of a linked list?

There are three types of linked lists:
1. Singly-linked list: We can only move forward in a singly-linked list.
2. Doubly-linked list: We can move forward as well as backward in this linked list.
3. Circular linked list: The last node contains the address/reference of the first (head)  in this linked list node.

What are the advantages of a linked list?

a) Linked list is dynamic in nature
b) Deletion and insertion are very fast in the linked list.
c) Memory is utilised efficiently in linked lists because we don’t need to declare size in advance.

What is a doubly-linked list?

A doubly linked list is one of the types of linked list in which each node consists of data and pointers to previous and the next nodes.

Can a doubly linked list be circular?

Yes, a doubly-linked list in which the last node and the head node are adjacent is said to be a circular doubly linked list.

Conclusion

In this article, we learnt about the advantages and disadvantages of a doubly linked list. We also got to know about the uses of double linked lists.  

If you want to learn more about implementing several operations in a doubly-linked list, you must check out Introduction and Implementation of Doubly Linked Lists. Some of the problems are based on doubly linked lists which you can solve are Reverse DLL nodes in groups, Rotate Doubly linked list by N nodes, Find the largest node in a Doubly Linked List and Check if a doubly-linked list of characters is palindrome or not etc.
To learn more about the Linked list, you can head over to the dedicated section of Linked List on our blog platform Library.

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