Queue in Data Structure — Types & Algorithms (with Examples)

A Queue is a linear data structure that follows the FIFO (First In, First Out) principle: the first element added is the first one removed.

Core Operations

• enqueue(item) — insert an element at the rear.
• dequeue() — remove and return the element at the front.
• peek() — view the front element without removing it.
• isEmpty() — check whether the queue has any elements.

Types of Queues

from collections import deque

class Queue:
    def __init__(self):
        self.items = deque()

    def enqueue(self, item):
        self.items.append(item)

    def dequeue(self):
        return self.items.popleft()

    def peek(self):
        return self.items[0]

    def is_empty(self):
        return len(self.items) == 0

Complexity

Applications

• Task and process scheduling in operating systems.
• Breadth First Search traversal in graphs.
• Handling of asynchronous data such as I/O buffers and print queues.