Queue in Dart

About

Queues in Dart are ordered collections optimized for adding/removing elements at both ends.
Unlike lists, they’re efficient for operations at beginning/end but not for random access.
They can store elements of the same type or mixed types.
Requires dart:collection library for queue operations.

Main Topics

Queue Creation

Definition: How to create and initialize queues in Dart.

Example:

import 'dart:collection';

void main() {
  // Creating an empty queue
  Queue<String> queue = Queue();

  // Creating from existing list
  Queue<String> fromList = Queue.from(['A', 'B', 'C']);
}

Queue Operations

Definition: Methods for adding, removing and accessing elements.

Example:

import 'dart:collection';

void main() {
  Queue<String> queue = Queue.from(['A', 'B']);

  // Adding elements
  queue.addLast('C');  // Add to end
  queue.addFirst('Z'); // Add to front

  // Removing elements
  queue.removeFirst();
  queue.removeLast();

  print(queue); // Outputs: {A, B}
}

Queue Types

Definition: Default Queue vs DoubleLinkedQueue.

Example:

import 'dart:collection';

void main() {
  // Default Queue
  Queue<int> defaultQueue = Queue();
  defaultQueue.addAll([1, 2, 3]);

  // DoubleLinkedQueue
  DoubleLinkedQueue<int> linkedQueue = DoubleLinkedQueue.from([4, 5, 6]);

  print(defaultQueue); // Outputs: {1, 2, 3}
  print(linkedQueue);  // Outputs: {4, 5, 6}
}

Queue Iteration

Definition: Techniques for looping through queue elements.

Example:

import 'dart:collection';

void main() {
  Queue<String> queue = Queue.from(['X', 'Y', 'Z']);

  // Using for loop
  for (var item in queue) {
    print(item);
  }

  // Using forEach
  queue.forEach((item) {
    print(item);
  });
}

Queue Methods

Definition: Common queue manipulation methods.

Example:

import 'dart:collection';

void main() {
  Queue<int> queue = Queue.from([10, 20, 30]);

  // Adding elements
  queue.addLast(40);
  queue.addFirst(5);

  // Removing elements
  queue.removeFirst();
  queue.removeLast();

  // Clearing queue
  queue.clear();

  print(queue); // Outputs: {}
}

How to Use

Creating: Use Queue() constructor or Queue.from()
Accessing: Use first and last properties or iteration
Modifying: Use addFirst, addLast, removeFirst, removeLast
Iterating: Use for-in loops or forEach

How It Works

Creation: Can initialize empty or from existing collections
Operations: Optimized for O(1) operations at both ends
Iteration: Maintains insertion order during iteration
Types: Default Queue is efficient for most cases

Example of Queue Operations:

import 'dart:collection';

void main() {
  Queue<String> queue = Queue.from(['First', 'Second']);

  // Modifying queue
  queue.addLast('Third');
  queue.addFirst('Zero');
  queue.removeFirst();

  // Iterating
  queue.forEach((item) {
    print(item); // Outputs: First, Second, Third
  });
}

Conclusion

A Queue in Dart is a specialized collection optimized for efficient insertion and removal at both ends. It excels in FIFO (First-In-First-Out) and LIFO (Last-In-First-Out) operations, offering better performance for these scenarios compared to lists while maintaining element insertion order.