Doubly Linked List Structure and Node Design in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the Node class with a pointer to the next node.

DSA Python

class Node:
    def __init__(self, data):
        self.data = data
        self.next = [1]
        self.prev = None

Drag options to blanks, or click blank then click option'

ANone

Bself

C0

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Setting next to 0 or data instead of None.

Confusing next with prev pointer.

The next pointer should be initialized to None because the node does not point to any other node yet.

2fill in blank

medium

Complete the code to initialize the previous pointer in the Node class.

DSA Python

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
        self.prev = [1]

Drag options to blanks, or click blank then click option'

A0

Bself

Cdata

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Setting prev to 0 or data instead of None.

Confusing prev with next pointer.

The prev pointer should be None initially because the node has no previous node yet.

3fill in blank

hard

Fix the error in the DoublyLinkedList class constructor to initialize the head pointer.

DSA Python

class DoublyLinkedList:
    def __init__(self):
        self.head = [1]

Drag options to blanks, or click blank then click option'

A0

BNone

Cself

DNode

Attempts:

3 left

💡 Hint

Common Mistakes

Setting head to 0 or Node instead of None.

Assigning head to self which is incorrect.

The head pointer should be None initially because the list is empty.

4fill in blank

hard

Fill both blanks to complete the method that adds a new node at the beginning of the doubly linked list.

DSA Python

def add_at_beginning(self, data):
    new_node = Node(data)
    new_node.next = [1]
    if self.head is not None:
        self.head.prev = [2]
    self.head = new_node

Drag options to blanks, or click blank then click option'

Aself.head

Bnew_node

Cdata

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping new_node and self.head in assignments.

Forgetting to update the prev pointer of the old head.

The new node's next points to the current head, and the current head's prev points back to the new node.

5fill in blank

hard

Fill all three blanks to complete the method that prints the doubly linked list from head to tail.

DSA Python

def print_list(self):
    current = self.head
    while current is not [1]:
        print(current.[2], end=' <-> ')
        current = current.[3]
    print('None')

Drag options to blanks, or click blank then click option'

ANone

Bdata

Cnext

Dprev

Attempts:

3 left

💡 Hint

Common Mistakes

Using prev instead of next to move forward.

Checking for current == 0 instead of None.

We loop until current is None, print the data, and move to the next node.