What is a Linked List ?

A linked list can be visualized as below:

If you look at the image provided above:

• You can see there are 4 Nodes (or cell), each with a partition in it:
  • The first partition represents data (A, B, C or you could store numbers [1,2,3] in them)
  • The second partition represents a pointer (next) to the next node/cell
• A Linked List is just a sequence of these Nodes
• The beginning Node of the Linked Lists is called a Head and the End Node of the linked list is called Tail

Python Code (We will be adding nodes, deleting nodes and printing the LinkedList):

# This is Node/Cell of a Linked List
# We will use this to create a new Node/Cell within the Linked List class below
# addToHead (add Node to beginning) and addToTail (add node to end) will use the Node class
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

class LinkedList:
    def __init__(self):
        self.head = None

    def addToHead(self, data):
        # Convert the provided data to a Node
        newData = Node(data)
        # Connect the newData node to pre-existing LinkedList
        newData.next = self.head
        self.head = newData

    def printLinkedList(self):
        # pointer to the Linked List as we want to parse through the entire LinkedList
        # and do not want to edit the linked list itself (hence don't directly use self.head)
        cur = self.head
        print('Printing...')
        while cur:
            print(cur.data)
            # move to the next node of LinkedList after printing the cur LinkedList node
            cur = cur.next

    def addToTail(self, data):
        newData = Node(data)
        cur = self.head

        # stop right before cur reach end (i.e: None)
        while cur.next:
            cur = cur.next

        cur.next = newData

    def deleteNode(self, data):
        # prev will be used once cur reaches the Node/data to skip over the cur Node/element
        prev = None
        cur = self.head

        while cur:
            if cur.data == data:
                break
            prev = cur
            cur = cur.next

        # if first Node is the data to be deleted then just move head to next Node
        if prev == None:
            self.head = self.head.next
        else:
            # skip over cur element
            prev.next = cur.next

Alright now that we have our LinkedList data structure created, lets call and create our LinkedList:

# Initiliaze an empty Linked list i.e: self.head = None
ll = LinkedList()

ll.addToHead(7)
ll.addToHead(5)
ll.addToHead(3)
ll.printLinkedList()

ll.addToTail(10)
ll.printLinkedList()

ll.deleteNode(5)
ll.printLinkedList()

ll.deleteNode(3)
ll.printLinkedList()

ll.deleteNode(10)
ll.printLinkedList()

And the Output should look like this for the above calls: