Looking At Linked Lists

Posted by Denise Pendleton-Lipinski on February 11, 2019

A linked list is a data structure that includes a ‘linked’ sequence of nodes. Each node contains data.

In a singly linked list each node points to the next node in the linked list:


In a doubly-linked list each node points to the next node as well as the previous node:


In order to access a single node you must traverse the entire linked list until you land on that node.

For example, to find node 4 we must start at node 1, move to node 2, then node 3, and finally to node 4:


This is very different from an array where each value can be found by using it’s index, or a dictionary (hash/object) where a value can be found using it’s key.

One benefit of a linked list is that you can add a node to the beginning of a linked list using constant time (O(1)). This means that subsequent nodes do not need to be re-indexed as they do in an array. The newest node simply becomes the “head” of the linked list.


Have you ever used linked lists in your applications?

If so why did you choose them over other data structures?