Standing in Line, Queue

A Queue is a data structure that resembles standing in line.

Just as the person who stands in line first gets served first, in a queue, the data that comes in first is processed first.

Due to this structure, a queue follows the principle of FIFO (First In, First Out), meaning "first in, first out."

How are queues used?

• Printer job queue: A printer processes print jobs in the order they were received.

• Call center queue: When a customer calls, they are added to a queue, and when an agent becomes free, they start by assisting the customer who has been waiting the longest.

Key Operations of a Queue

The key operations frequently used with a queue are as follows:

• enqueue: The operation to add new data to the end of the queue.

• dequeue: The operation to remove and return data from the front of the queue.

• peek: The operation to check the data at the front of the queue without removing it.

• is_empty: The operation to check if the queue is empty.

Implementing a Queue in Python

By using the append() method to add data and the pop(0) method to remove data, a basic queue can be implemented with a list.

Queue Implementation Example in Python

class Queue:
    # Initialize the queue
    def __init__(self):
        self.queue = []

    # Add data to the queue
    def enqueue(self, item):
        self.queue.append(item)
        print(f"Enqueue: {item} has been added to the queue.")

    # Remove data from the queue
    def dequeue(self):
        if not self.is_empty():
            item = self.queue.pop(0)
            print(f"Dequeue: {item} has been removed from the queue.")
            return item
        else:
            print("Dequeue: The queue is empty.")
            return None

    # Check the data at the front of the queue
    def peek(self):
        if not self.is_empty():
            return self.queue[0]
        else:
            print("Peek: The queue is empty.")
            return None

    # Check if the queue is empty
    def is_empty(self):
        return len(self.queue) == 0

# Queue usage example
my_queue = Queue()
my_queue.enqueue(1) # Enqueue: 1 has been added to the queue.
my_queue.enqueue(2) # Enqueue: 2 has been added to the queue.

print(f"Peek: The item at the front of the queue is {my_queue.peek()}.")

my_queue.dequeue()  # Dequeue: 1 has been removed from the queue.
my_queue.dequeue()  # Dequeue: 2 has been removed from the queue.
my_queue.dequeue()  # The queue is empty, cannot remove item.

In Summary

• A queue is a data structure that follows the FIFO (First In, First Out) principle.

• Key operations include enqueue (add), dequeue (remove), peek (check data), and is_empty (check if empty).

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