What is Queue?

Question

What is Queue in detail?

Abhay Shanker · Answer

Queue is a FIFO collection. It processes elements in a first-in first-out order. The following table lists some of the commonly used methods of the Queue class The following example demonstrates use of Stack: using System; using System.Collections; namespace CollectionsApp { class Program { static void Main(string[] args) { Queue q = new Queue(); q.Enqueue('A'); q.Enqueue('B'); q.Enqueue('C'); q.Enqueue('D'); Console.WriteLine(Current queue: ); foreach (char c in q) Console.Write(c +  ); Console.WriteLine(); q.Enqueue('E'); q.Enqueue('E'); Console.WriteLine(Current queue: ); foreach (char c in q) Console.Write(c +  ); Console.WriteLine(); Console.WriteLine(Removing some values ); char ch = (char)q.Dequeue(); Console.WriteLine(The removed value: {0} ch); ch = (char)q.Dequeue(); Console.WriteLine(The removed value: {0} ch); Console.ReadKey(); } } } When the above code is compiled and executed it produces the following result: Current queue: A B C D Current queue: A B C D E F Removing values The removed value: A The removed value: B

Vulpes · Answer

It's a data structure from which items can only be removed in the order in which they're added. So the first item added is the first to be removed. This is called a 'first in first out' or FIFO data structure. .NET has both generic and non-generic implementations of a queue. Where the items are all of the same type the generic implementation (System.Colloections.Generic.Queue ) should be preferred. Both classes provide (amongst others) the following methods: Enqueue - to add a new item to the tail of the queue. Dequeue - to retrieve and remove the item at the head of the queue. Peek - to retrieve the item at the head of the queue without removing it. There's also a Count property so you can check whether there's any items in the queue before attempting to retrieve the head one. Here's a simple example of use: using System; using System.Collections.Generic; class Program { static void Main() { var persons = new Queue (); persons.Enqueue(David); persons.Enqueue(Vulpes); Console.WriteLine(persons.Dequeue()); if (persons.Count > 0) { Console.WriteLine(persons.Peek()); } Console.WriteLine(persons.Count); Console.ReadKey(); } } The output is: David Vulpes 1