Circular Queue Implementation Using Array in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the front pointer of the circular queue.

DSA Python

class CircularQueue:
    def __init__(self, size):
        self.size = size
        self.queue = [None] * size
        self.front = [1]
        self.rear = -1

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

A-1

B0

CNone

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting front to 0 initially causes confusion between empty and full states.

The front pointer is initialized to -1 to indicate the queue is empty initially.

2fill in blank

medium

Complete the code to check if the circular queue is full.

DSA Python

def is_full(self):
    return (self.rear + 1) % self.size == [1]

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

A-1

Bself.rear

C0

Dself.front

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing with rear or 0 instead of front causes wrong full condition.

The queue is full when the next position of rear is front.

3fill in blank

hard

Fix the error in the enqueue method to update the rear pointer correctly.

DSA Python

def enqueue(self, data):
    if self.is_full():
        print("Queue is full")
        return
    if self.front == -1:
        self.front = 0
    self.rear = [1]
    self.queue[self.rear] = data

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

Aself.rear + 1

B(self.rear + 1) % self.size

Cself.rear - 1

Dself.front + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Incrementing rear without modulo causes index out of range errors.

The rear pointer must move forward circularly using modulo to wrap around.

4fill in blank

hard

Fill both blanks to correctly update the front pointer in the dequeue method.

DSA Python

def dequeue(self):
    if self.front == -1:
        print("Queue is empty")
        return None
    data = self.queue[self.front]
    if self.front == self.rear:
        self.front = [1]
        self.rear = [2]
    else:
        self.front = (self.front + 1) % self.size
    return data

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

A-1

B0

Cself.rear

Dself.front

Attempts:

3 left

💡 Hint

Common Mistakes

Setting front or rear to 0 instead of -1 causes incorrect empty state.

When the last element is dequeued, both front and rear reset to -1 to indicate empty queue.

5fill in blank

hard

Fill in the blanks to complete the display method that prints the queue elements in order.

DSA Python

def display(self):
    if self.front == -1:
        print("Queue is empty")
        return
    i = self.front
    while True:
        print(self.queue[i], end=" ")
        if i == self.rear:
            break
        i = (i [1] 1) [2] self.size
    print()

# Example usage:
cq = CircularQueue(5)
cq.enqueue(10)
cq.enqueue(20)
cq.enqueue(30)
cq.display()  # Output: 10 20 30

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

A+

B-

C%

D//

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or floor division causes wrong index updates.

To move forward circularly, add 1 and take modulo with size.