Doubly Linked List

The linked list is a versatile data structure, free from the "holes" inherent in arrays.
Manipulating the first element is efficient, but for certain abstract data types like queues, efficient manipulation of the last element and bidirectional traversal are needed. Standard linked lists struggle with accessing the last element, requiring O(N) time complexity.
Doubly linked lists resolve this limitation and offer solutions to various other challenges.

from lolviz import *

from IPython.display import display_png

class Node:

def __init__(self, data):

self.value = data

self.next = None

self.previous = None

# Let's create some nodes

node1 = Node(1)

node2 = Node(2)

node3 = Node(3)

# Then let's couple them into a linked list

node1.next = node2

node2.next = node3

# And don't forget to assign the reference to a previous node

node2.previous = node1

node3.previous = node2

display_png(objviz(node1))


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from lolviz import *
from IPython.display import display_png

class Node:

  def __init__(self, data):
    self.value = data
    self.next = None
    self.previous = None

# Let's create some nodes
node1 = Node(1)
node2 = Node(2)
node3 = Node(3)

# Then let's couple them into a linked list
node1.next = node2
node2.next = node3
# And don't forget to assign the reference to a previous node
node2.previous = node1
node3.previous = node2

display_png(objviz(node1))

The doubly linked list's nodes contain the references to the next and to the previous elements. Therefore we can access the first and the last item in O(1) constant running time. Time complexity of all other operations for doubly linked list is the same as for the simple linked list.

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def search(self, value):
    # Start the search from the head of the linked list
    current = self.head
    # Traverse the linked list
    while current:
        # Check if the value of the current node matches the target value
        if current.data == value:
            # Return the node if found
            return current
        # Move to the next node
        current = current.next
    # Return None if the value is not found in the linked list
    return None

def insert(self, value):
    # Create a new node with the given value
    new_node = ListNode(value)
    # Check if the linked list is empty
    if not self.head:
        # If the linked list is empty, set the new node as the head
        self.head = new_node
    else:
        # If the linked list is not empty, insert the new node at the beginning
        new_node.next = self.head
        self.head.prev = new_node
        self.head = new_node

def delete(self, value):
    # Start the search from the head of the linked list
    current = self.head
    # Traverse the linked list
    while current:
        # Check if the value of the current node matches the target value
        if current.data == value:
            # Update the pointers of the surrounding nodes to skip the current node
            if current.prev:

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