What is a Queue?

A queue is a data structure that follows First-In-First-Out (FIFO) — like a line at a store. The first person in line is the first person served. New people join at the back, and people leave from the front.

Operations:

• Enqueue: Add an item to the back (rear)
• Dequeue: Remove and return the front item
• Front/Peek: Look at the front item without removing it
• IsEmpty: Check if the queue is empty

Types:

• Simple queue: Basic FIFO
• Priority queue: Items with higher priority go first
• Circular queue: Wraps around when full
• Double-ended queue (Deque): Can add/remove from both ends

Common Uses:

• Task scheduling: Process tasks in order
• Message queues: Handle messages between services
• Breadth-first search: Explore graph level by level
• Print queues: Print documents in order

FAQ

What's the difference between a queue and a stack?

Queue is FIFO (first in, first out). Stack is LIFO (last in, first out).

What's a priority queue?

A queue where items have priorities. Higher priority items are served first, even if they arrived later.