Understanding Queue Data Structure

Sep 11, 2024

Notes on Queue Data Structure Lecture

Introduction

  • Presenter: Tanmay from Simple Snippets
  • Topic: Queue Data Structure
  • Structure of video:
    • Theory of queue data structure
    • Visual representation and operations
    • C++ implementation in part two of the series

What is a Queue?

  • Definition:
    • A linear data structure where data is inserted/retrieved in a sequential manner.
    • Operates on a First In First Out (FIFO) principle.
    • Opposite of Stack (LIFO - Last In First Out).
  • Real-world analogy:
    • Similar to a line of cars or people waiting, where the first to arrive is the first to be served.

Characteristics of Queue

  • Abstract data type with a bounded capacity.
  • Allows adding and removing elements in a specific order (FIFO).
  • Key Operations:
    1. Enqueue (NQ): Add an element to the rear.
    2. Dequeue (DQ): Remove an element from the front.
    3. Check if full: Is the queue full?
    4. Check if empty: Is the queue empty?
    5. Count: How many elements are in the queue?

Visual Representation

  • Computer Memory:
    • Each memory location has a unique address (e.g., 1000, 1001, etc.).
    • Queue is represented as a rectangular box in memory.
  • Ends of the Queue:
    • Front: Where elements are removed.
    • Rear: Where elements are added.

Operations in Detail

Enqueue (NQ)

  • Process:
    1. Check if the queue is full.
    2. If empty, set rear and front to 0.
    3. Add element at the rear and increment rear.
    4. If not empty, only increment rear.

Dequeue (DQ)

  • Process:
    1. Check if the queue is empty.
    2. If there's one element (front == rear), set both to -1.
    3. If multiple elements exist, remove from front and increment front.

Conditions to Check

  • Is Empty: If front and rear both are -1.
  • Is Full: If rear equals size of the array - 1.

Implementation Strategy

  • Using arrays to implement the queue.
  • Initialization: Set rear and front to -1.
  • Maintain two variables to track the current positions of front and rear.

Applications of Queue

  • Common Uses:
    • CPU scheduling (process execution order).
    • Disk scheduling & handling interrupts in real-time.
    • Call center systems (handling calls in order).
    • Data transfer synchronization.

Conclusion

  • Understanding queues is vital as they are widely used in real-life scenarios and computing.
  • Next video will cover actual implementation of queue operations in C++.