Singly Linked List Vs Doubly Linked List

   Last Updated: 20 January, 2025       🕓  5 Mins Read

Hey, In this article you are going to learn difference between Singly Linked List and Doubly Linked List in terms of their structure, memeory uses, performance, implementation and more.

After learning, you will have a comprehensive understanding of when to use a Singly Linked List over a Doubly Linked List.

What is Singly Linked List?

A Singly Linked List is a linear (ordered) data structure that contains a collection of elements, and each element is connected to its next element in a sequence.

Each element in a singly linked list is called a Node. The node consists of two fields: a data field and the reference field (address of the next node).

There is a HEAD pointer, which points to the first node of the singly linked list, and if the list is empty, then it stores NULL and the last node is called the Tail, and it stores NULL in the reference field (next).

A singly linked list can traverse only in the forward direction because each node contains the address of the next node.

Advantages of Singly Linked List

• Dynamic data structure
• No memory wastage
• Easy Implementation
• Insertion and Deletion Operations
• Flexible
• Efficient for large data
• Scalability

Disadvantages of Singly Linked List

• Random access is inefficient
• Additional memory required for pointers
• Potential for memory fragmentation
• Potential for Memory Leaks

What is Doubly Linked List in Data Structure?

A doubly linked list is a linear data structure; it is another form of Linked List.

A doubly linked list is a collection of seqential nodes (elements); each node consists of three fields: two pointer fields (references to the previous and to the next node in the sequence of nodes) and one data field.

A double linked list can be traversed in forward and backward directions because each node has two pointers, previous and next.

In the Doubly Linked List, each node consist of three parts:

1. First Part: Pointer to point the previous node in the list.
2. Second Part: The data (value) stored in the node.
3. Third Part: Pointer to point the next node in the list.

Advantages of Doubly Linked List

• Dynamic data structure
• Bidirectional Traversal
• Dynamic size
• Simpler Insertion and Deletion
• Effective memory management
• Efficient Operations at Both Ends

Disadvantages of Doubly Linked List

• Occupy more memory
• Difficulty in pointer management
• Slower Operations
• Memory Management Overhead

Difference between Singly Linked List and Doubly Linked List

Let’s know about some major differences between the Singly Linked List and the Doubly Linked List in data structure.

Characteristic	Singly Linked List	Doubly Linked List
Node structure	Each node consists of two parts: data and reference to the next node.	Each node consists of three parts: data, previous and next node references.
Memory Usage	It occupies less memory because each node contains only one reference.	It occupies more memory as each node contains two references (previous and next nodes).
Direction of Traversal	It can traverse only in one direction, which is a farward direction.	It can traverse both farward and backward directions.
Implementation Complexity	Compared to doubly linked lists, singly linked lists implementation is simple because each node contains only one reference.	Its implementation is a bit complex because each node contains two references, requiring more management and care in code.
Use Case	Good choice if memory is a concern and traversal is required only in a farward direction.	Preferred when frequent operations require elements to be accessed from both ends.
Operations	Typically slower for operations that involve elements at the end of the list.	Faster for operations involving the end of the list due to the tail pointer.
Complexity	The complexity of insertion and deletion is O(n).	The complexity of insertion and deletion is O(1).