Implement Stack Using Queue in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the queue in the stack constructor.

DSA Python

import collections
class StackUsingQueue:
    def __init__(self):
        self.queue = [1]

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Alist()

B[]

Ccollections.deque()

Dqueue.Queue()

Attempts:

3 left

💡 Hint

Common Mistakes

Using a plain list which is inefficient for queue operations.

Using queue.Queue() which is for threading and not needed here.

We use collections.deque() because it provides efficient queue operations.

2fill in blank

medium

Complete the code to add an element to the stack using the queue.

DSA Python

def push(self, x):
    self.queue.append(x)
    for _ in range(len(self.queue) - 1):
        self.queue.append([1])

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Aself.queue.popitem()

Bself.queue.pop(0)

Cself.queue.pop()

Dself.queue.popleft()

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() which removes from the end, not the front.

Using pop(0) on deque which is invalid.

We use popleft() to remove the front element and append it to the back, rotating the queue.

3fill in blank

hard

Fix the error in the pop method to remove and return the top element of the stack.

DSA Python

def pop(self):
    if not self.queue:
        return None
    return self.queue.[1]()

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Apopleft

Bpop

Cremove

Ddequeue

Attempts:

3 left

💡 Hint

Common Mistakes

Using popleft() which removes from the front, not the top.

Using remove() which requires a value, not an index.

After rotation in push, the top element is at the end, so pop() removes it.

4fill in blank

hard

Fill both blanks to implement the top method that returns the top element without removing it.

DSA Python

def top(self):
    if not self.queue:
        return None
    return self.queue[1]

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

A[-1]

B[0]

C.pop()

D.popleft()

Attempts:

3 left

💡 Hint

Common Mistakes

Using [0] which accesses the front, not the top.

Using .pop() which removes the element.

The top element is at the end of the queue, so access it with [-1].

5fill in blank

hard

Fill all three blanks to implement the empty method that checks if the stack is empty.

DSA Python

def empty(self):
    return [1] == [2]

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

Alen(self.queue)

B0

C[]

Dself.queue

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing the queue object directly to an empty list.

Using self.queue == 0 which is invalid.

Check if the length of the queue is zero to determine if the stack is empty.