Dequeue Using Linked List in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a new node at the front of the dequeue.

DSA Python

def add_front(self, data):
    new_node = Node(data)
    if self.front is None:
        self.front = self.rear = new_node
    else:
        new_node.next = [1]
        self.front.prev = new_node
        self.front = new_node

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

Aself.front

Bself.rear

Cnew_node

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Setting new_node.next to None instead of the current front.

Confusing front and rear pointers.

The new node's next should point to the current front node.

2fill in blank

medium

Complete the code to remove a node from the rear of the dequeue.

DSA Python

def remove_rear(self):
    if self.rear is None:
        return None
    data = self.rear.data
    self.rear = self.rear.prev
    if self.rear is not None:
        self.rear.next = [1]
    else:
        self.front = None
    return data

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

ANone

Bself.front

Cself.rear

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Setting rear.next to rear itself causing a cycle.

Not updating front when list becomes empty.

After removing the rear node, if rear exists, its next should be None.

3fill in blank

hard

Fix the error in the code to add a node at the rear of the dequeue.

DSA Python

def add_rear(self, data):
    new_node = Node(data)
    if self.rear is None:
        self.front = self.rear = new_node
    else:
        self.rear.next = new_node
        new_node.prev = [1]
        self.rear = new_node

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

Aself.front

Bself.rear

Cnew_node

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Setting new_node.prev to new_node causing self-reference.

Setting new_node.prev to front instead of rear.

The new node's prev should point to the current rear before updating rear.

4fill in blank

hard

Fill both blanks to correctly remove a node from the front of the dequeue.

DSA Python

def remove_front(self):
    if self.front is None:
        return None
    data = self.front.data
    self.front = self.front.[1]
    if self.front is not None:
        self.front.[2] = None
    else:
        self.rear = None
    return data

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

Anext

Bprev

Cfront

Drear

Attempts:

3 left

💡 Hint

Common Mistakes

Setting front to front.prev which moves backward incorrectly.

Not clearing the prev pointer of the new front node.

To remove the front node, move front to front.next and set new front's prev to None.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps each node's data to its position if data is positive.

DSA Python

def map_positive_nodes(self):
    result = {node.data[1]: idx for idx, node in enumerate(self.iterate()) if node.data [2] 0 and node.data is not [3] None}
    return result

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

A * 2

B>

C==

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' instead of '+' for key expression.

Using '==' instead of '>' for filtering positive data.

Checking data is None with '==' instead of 'is not'.

The comprehension maps node.data plus idx as key, filters nodes with data > 0, and excludes None data.