An adjacency list is, in essence, a list of linked lists where each vertex of the graph is stored alongside a collection of connected vertices:įurther reading: Python’s implementation of dynamic arrays is quite interesting and definitely worth reading about. There are different ways to implement graphs like the above, but one of the most common is to use an adjacency list. For example, a visual representation of a graph-say a directed acyclic graph (DAG)-might look like this: Directed Acyclic Graph Graphs can be used to show relationships between objects or to represent different types of networks. You’ll see examples of these implementations later in the article. Since stacks use the LIFO approach, the last element inserted (at the top) will be the first to be retrieved.īecause of the way you insert and retrieve elements from the edges of queues and stacks, linked lists are one of the most convenient ways to implement these data structures.
In the above diagram you can see that the first element inserted on the stack (index 0) is at the bottom, and the last element inserted is at the top. When you retrieve elements, they’ll be taken from the front of the queue.įor a stack, you use a Last-In/Fist-Out (LIFO) approach, meaning that the last element inserted in the list is the first to be retrieved: Stack When you append new elements to the queue, they’ll go to the rear end. In the diagram above, you can see the front and rear elements of the queue. That means that the first element inserted in the list is the first one to be retrieved: Queue For a queue, you use a First-In/First-Out (FIFO) approach. Queues and stacks differ only in the way elements are retrieved. They’re also useful for much more complex tasks, such as lifecycle management for an operating system application. They can be used to implement ( spoiler alert!) queues or stacks as well as graphs. Linked lists serve a variety of purposes in the real world. Now that you know how a linked list is structured, you’re ready to look at some practical use cases for it. The last node must have its next reference pointing to None to determine the end of the list. The first node is called the head, and it’s used as the starting point for any iteration through the list. Here’s what a typical node looks like: NodeĪ linked list is a collection of nodes.
Before going more in depth on what linked lists are and how you can use them, you should first learn how they are structured.
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