Queue Implementation using Array 🚀

beginner

17 min

Queue Implementation using Array 🚀

Welcome to another exciting tutorial! Today, we're going to learn how to implement a Queue using an Array 📝. This data structure is essential for handling tasks that come in sequentially but need to be processed in the order they arrive. Let's dive in!

What is a Queue? 💡

A Queue is a collection of elements ordered in a sequential manner where the addition and removal of elements follows a specific rule: elements are added at the back (rear) and removed from the front (front). This order is often referred to as First-In-First-Out (FIFO).

Why use a Queue? 🎯

Queues are useful in various scenarios such as managing tasks in an operating system, handling requests in a web server, and optimizing graph traversal algorithms. Let's get our hands dirty and implement a Queue using an Array!

Queue Implementation 📝

Data Representation

To represent a Queue, we'll use an Array, and two additional variables: front and rear, which keep track of the position of the first and last elements in the queue, respectively.

python

queue = []
front = -1
rear = -1

Functions

We'll create three main functions: enqueue, dequeue, and is_empty.

enqueue(item): Adds an item to the rear of the queue.

python

def enqueue(item):
    global queue, rear
    queue.append(item)
    rear += 1

dequeue(): Removes and returns the front item from the queue.

python

def dequeue():
    global queue, front, rear
    if is_empty():
        return None
    front += 1
    item = queue[front]
    queue[front] = None
    if front > rear:
        front = rear = -1
    return item

is_empty(): Checks if the queue is empty.

python

def is_empty():
    return front == -1

Practical Example 💼

Imagine you're running a small print shop. Customers arrive and place orders one after the other. You will process the orders in the order they were received (FIFO).

python

queue = []
customers = ['Alice', 'Bob', 'Charlie', 'David', 'Eve']

for customer in customers:
    enqueue(customer)

while not is_empty():
    print('Printing:', dequeue())

Output:

Printing: Alice
Printing: Bob
Printing: Charlie
Printing: David
Printing: Eve

Quiz Time 🤓

Quick Quiz

Question 1 of 1

What is the main difference between a Queue and a Stack?

Quick Quiz

Question 1 of 1

What happens if you try to `dequeue()` from an empty Queue?