Create and Initialize Doubly Linked List in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a Node class with a constructor.

DSA Python

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

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

Aprev

Btail

Chead

Dnext

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'head' or 'tail' as node attributes instead of 'next'.

Confusing 'prev' and 'next' pointers.

The 'next' attribute points to the next node in the doubly linked list.

2fill in blank

medium

Complete the code to initialize an empty DoublyLinkedList class.

DSA Python

class DoublyLinkedList:
    def __init__(self):
        self.head = None
        self.[1] = None

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

Atail

Bdata

Cprev

Dnext

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'next' or 'prev' as attributes of the list instead of nodes.

Forgetting to initialize the tail pointer.

The 'tail' attribute points to the last node in the doubly linked list.

3fill in blank

hard

Fix the error in the method to add a node at the beginning of the list.

DSA Python

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

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

Ahead

Bnext

Cprev

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Setting 'next' pointer instead of 'prev' on the old head.

Not updating the tail when list was empty.

When adding at the beginning, the old head's 'prev' pointer should point to the new node.

4fill in blank

hard

Fill both blanks to complete the method that adds a node at the end of the list.

DSA Python

def add_at_end(self, data):
    new_node = Node(data)
    if self.head is None:
        self.head = new_node
        self.tail = new_node
    else:
        self.tail.[1] = new_node
        new_node.[2] = self.tail
        self.tail = new_node

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

Anext

Bprev

Chead

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping 'next' and 'prev' pointers.

Not updating the tail pointer to the new node.

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

5fill in blank

hard

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

DSA Python

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

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

Adata

Bnext

Cprev

Dhead

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' instead of 'next' to move forward.

Printing 'prev' data instead of current node's data.

We print the 'data' of current node, check if 'next' exists to print arrow, and move to 'next' node.