Queues

Queues follow FIFO (First In First Out) principle. Elements are added at the rear and removed from the front.

Animated Visualization

Step 1 of 5

Front

Rear

Initial queue: [10, 20, 30] - Front: 10, Rear: 30

javascript

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// Queue Implementation using Array
class Queue {
  constructor() {
    this.items = [];
  }
  // Add element to rear
  enqueue(element) {
    this.items.push(element);
  }
  // Remove element from front
  dequeue() {
    if (this.isEmpty()) {
      return "Queue is empty";
    }
    return this.items.shift();
  }
  // View front element
  front() {
    if (this.isEmpty()) {
      return "Queue is empty";
    }
    return this.items[0];
  }
  // Check if queue is empty
  isEmpty() {
    return this.items.length === 0;
  }
  // Get queue size
  size() {
    return this.items.length;
  }
  // Time Complexity:
  // Enqueue: O(1)
  // Dequeue: O(n) with array, O(1) with linked list
  // Front: O(1)
  // Search: O(n)

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Explanation

Queues are linear data structures that follow the FIFO principle. They're used in task scheduling, BFS algorithms, and request handling systems. Enqueue adds to rear, dequeue removes from front.

Operations & Complexity

EnqueueO(1)

Add element to rear

DequeueO(1)

Remove element from front

FrontO(1)

View front element

SearchO(n)

Must traverse queue

Time Complexity