Circular queue in Data Structures Theory - Mini Project: Build & Apply

Understanding Circular Queue

📖 Scenario: Imagine you are managing a small parking lot with a fixed number of parking spaces arranged in a circle. Cars enter and leave the lot in order, and when the lot is full, new cars must wait until a space is free. This setup works like a circular queue.

🎯 Goal: Build a simple circular queue model using a list and pointers to track the front and rear positions. You will create the data structure, set up control variables, implement the logic to add and remove cars, and finalize the queue management.

📋 What You'll Learn

Create a list called parking_lot with 5 empty slots represented by None

Create two variables called front and rear both set to -1

Write a function called enqueue(car) that adds a car to the circular queue if space is available

Write a function called dequeue() that removes a car from the circular queue if it is not empty

💡 Why This Matters

🌍 Real World

Circular queues are used in real-world systems like traffic lights, CPU scheduling, and buffering data streams where resources are reused in a cycle.

💼 Career

Understanding circular queues helps in software development roles involving system design, embedded systems, and performance optimization.

1

Create the parking lot list

Create a list called parking_lot with exactly 5 slots, each initialized to None to represent empty parking spaces.

Data Structures Theory

# Create the parking_lot list with 5 None values
# Your code here

Need a hint?

Use square brackets to create a list with 5 None elements.

2

Set up front and rear pointers

Create two variables called front and rear and set both to -1 to indicate the queue is initially empty.

Data Structures Theory

parking_lot = [None, None, None, None, None]
# Initialize front and rear pointers
# Your code here

Need a hint?

Set both front and rear to -1 to show the queue is empty.

3

Write the enqueue function

Write a function called enqueue(car) that adds a car to the parking_lot circular queue. It should update rear and handle wrapping around. If the queue is full, do nothing.

Data Structures Theory

parking_lot = [None, None, None, None, None]
front = -1
rear = -1

# Define enqueue function to add a car
# Your code here

Need a hint?

Use modulo % to wrap rear around the list length.

4

Write the dequeue function

Write a function called dequeue() that removes a car from the parking_lot circular queue. It should update front and handle wrapping around. If the queue is empty, do nothing.

Data Structures Theory

parking_lot = [None, None, None, None, None]
front = -1
rear = -1

def enqueue(car):
    global front, rear
    if (rear + 1) % len(parking_lot) == front:
        return  # Queue is full
    if front == -1:
        front = 0
    rear = (rear + 1) % len(parking_lot)
    parking_lot[rear] = car

# Define dequeue function to remove a car
# Your code here

Need a hint?

Reset front and rear to -1 when queue becomes empty.