Introduction to Queues

A Queue is a linear data structure that follows the First-In, First-Out (FIFO) principle. This means that the first element added to the queue will be the first one to be removed.

Queues are commonly used in programming for tasks such as managing requests in a web server, scheduling tasks, and implementing breadth-first search algorithms.

Interactive Queue Visualization

The visualization below demonstrates the basic operations of a queue. You can see how elements are enqueued at the rear and dequeued from the front.

Queue Visualization (FIFO)

Current Step

1 of 11

Last Operation

Ready to start

Queue Size

Queue operations will appear here...

Queue Visualization

FRONT ← Elements ← REAR

FRONT →

← REAR

DequeueFlow DirectionEnqueue

Front Element

Next to be dequeued

Rear Element

Last enqueued

Array View

[10,20,30]

front: index 0|rear: index 2

ENQUEUE

Add to rear

DEQUEUE

Remove from front

👁

PEEK

View front (no remove)

Queue (FIFO): Elements are added at the rear and removed from the front. Like a line at a store - first person in line is first to be served! Enqueue adds to rear, dequeue removes from front. All operations are O(1) time complexity. This demo auto-resets to keep cycling through operations.

Queue Data Structure

A Queue is a linear data structure that follows the First-In, First-Out (FIFO) principle. It's like a line of people waiting for a bus: the first person to get in line is the first person to get on the bus.

Key Operations

Enqueue: Adds an element to the back of the queue.
Dequeue: Removes the front element from the queue.
Peek/Front: Returns the front element without removing it.
isEmpty: Checks if the queue is empty.

Queue Implementation


from collections import deque

# Using a deque as a queue
queue = deque()

# Enqueue
queue.append(1)
queue.append(2)
queue.append(3)

# Dequeue
front_element = queue.popleft()  # 1

# Peek
front_element = queue[0]  # 2

# isEmpty
if not queue:
    print("Queue is empty")