What is the key difference between a singly and a doubly linked list?

In a singly linked list, each node has one reference, next, so you can move only forward. In a doubly linked list, each node also has a prev reference, so you can move forward and backward.

Show the node class for both lists in Java.

Java example: class SinglyNode { int data; SinglyNode next; SinglyNode(int data) { this.data = data; } } class DoublyNode { int data; DoublyNode prev; DoublyNode next; DoublyNode(int data) { this.data = data; } }

Which list uses more memory?

The doubly linked list, because every node stores an extra prev reference. For n nodes that is n extra references, which matters when the list is large and the data in each node is small.

Why is deleting a given node faster in a doubly linked list?

To delete a node you must update the node before it. In a doubly linked list you reach it directly through prev, so the delete is O(1). In a singly linked list you must walk from the head to find the previous node, which is O(n):

Can both lists be traversed in reverse order?

A doubly linked list can, by starting at the tail and following prev. A singly linked list cannot move backward; to print it in reverse you need recursion or a stack, which uses O(n) extra space:

Which is simpler to implement?

The singly linked list. Every insert or delete in a doubly linked list must update two links per neighbour ( next and prev ), so there are more cases where a mistake can break the list.

When should you choose a singly linked list?

Choose a singly linked list when you only move forward, memory is tight, and operations happen mainly at the head, for example in a stack, an adjacency list of a graph, or hash table chaining.

When should you choose a doubly linked list?

Choose a doubly linked list when you need to move in both directions or delete nodes you already hold references to, for example in an LRU cache, a browser's back and forward history, or a text editor's undo and redo.

Which type is java.util.LinkedList?

java.util.LinkedList is a doubly linked list. That is why it supports descendingIterator() and O(1) removeLast().

Compare the complexity of their operations.

Insert at head: both O(1). Insert at tail with a tail reference: both O(1). Delete the tail: singly O(n), because the second-last node must be found; doubly O(1). Delete a given node: singly O(n), doubly O(1). Search: both O(n).

Difference between Singly Linked List and Doubly Linked List

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:

First Part: Pointer to point the previous node in the list.
Second Part: The data (value) stored in the node.
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