08 Aug C# Queue
Queue Collections come under System.Collection.Generic namespace. It stores in the FIFO form i.e. First In First Out, unlike Stack which stores in the LIFO form. Enqueue is when data is inserted in the queue, whereas Dequeue is when it is removed.
Create a Queue and Enqueue
Add elements in the Queue with the Enqueue() method in C#. Enqueue means inserting elements to the end of the queue. To create a Queue in C#, with string elements, use <string>. Set the type in angular braces as shown below:
Queue<string> queue = new Queue<string>();
Let us see an example and create a queue with some string elements:
using System;
using System.Collections.Generic;
namespace Studyopedia
{
class Program
{
static void Main(string[] args)
{
// Create a queue
Queue<string> queue = new Queue<string>();
// Insert 5 elements to the Queue
queue.Enqueue("Amphibians");
queue.Enqueue("Reptiles");
queue.Enqueue("Mammals");
queue.Enqueue("Fish");
queue.Enqueue("Birds");
// Display the elements
Console.WriteLine("Display the queue elements...\n");
foreach (string s in queue)
{
Console.WriteLine(s);
}
}
}
}
Output
Display the queue elements... Amphibians Reptiles Mammals Fish Birds
Dequeue
To return the first element (beginning of the queue) from the queue and remove it, use the Dequeue() method in C#. Let us see an example:
using System;
using System.Collections.Generic;
namespace Studyopedia
{
class Program
{
static void Main(string[] args)
{
// Create a queue
Queue<string> queue = new Queue<string>();
// Insert 5 elements to the Queue
queue.Enqueue("Amphibians");
queue.Enqueue("Reptiles");
queue.Enqueue("Mammals");
queue.Enqueue("Fish");
queue.Enqueue("Birds");
// Display the elements
Console.WriteLine("Display the queue elements...");
foreach (string s in queue)
{
Console.WriteLine(s);
}
// Removes the first element from the Queue
queue.Dequeue();
// Display the updated elements
Console.WriteLine("\nDisplay the updated queue elements...");
foreach (string s in queue)
{
Console.WriteLine(s);
}
}
}
}
Output
Display the queue elements... Amphibians Reptiles Mammals Fish Birds Display the updated queue elements... Reptiles Mammals Fish Birds
Count the number of elements
The Count property is used to count the number of elements in the Queue. Let us see an example:
using System;
using System.Collections.Generic;
namespace Studyopedia
{
class Program
{
static void Main(string[] args)
{
// Create a queue
Queue<string> queue = new Queue<string>();
// Insert 5 elements to the Queue
queue.Enqueue("Amphibians");
queue.Enqueue("Reptiles");
queue.Enqueue("Mammals");
queue.Enqueue("Fish");
queue.Enqueue("Birds");
// Display the elements
Console.WriteLine("Display the queue elements...");
foreach (string s in queue)
{
Console.WriteLine(s);
}
// Display the count of elements
Console.WriteLine("\nNumber of elements = "+queue.Count);
}
}
}
Output
Display the queue elements... Amphibians Reptiles Mammals Fish Birds Number of elements = 5
Check for an element in the queue
The Contains() method is used to check whether an element exists in the queue or not. Let us see an example:
using System;
using System.Collections.Generic;
namespace Studyopedia
{
class Program
{
static void Main(string[] args)
{
// Create a queue
Queue<string> queue = new Queue<string>();
// Insert 5 elements to the Queue
queue.Enqueue("Amphibians");
queue.Enqueue("Reptiles");
queue.Enqueue("Mammals");
queue.Enqueue("Fish");
queue.Enqueue("Birds");
// Display the elements
Console.WriteLine("Display the queue elements...");
foreach (string s in queue)
{
Console.WriteLine(s);
}
// Check for an element in the Queue
Console.WriteLine("\nAre Mammals in the Queue? = "+queue.Contains("Mammals"));
}
}
}
Output
Display the queue elements... Amphibians Reptiles Mammals Fish Birds Are Mammals in the Queue? = True
Peek an element
To return the first element from the top of the queue, without removing it, use the Peek() method. Let us see an example:
using System;
using System.Collections.Generic;
namespace Studyopedia
{
class Program
{
static void Main(string[] args)
{
// Create a queue
Queue<string> queue = new Queue<string>();
// Insert 5 elements to the Queue
queue.Enqueue("Amphibians");
queue.Enqueue("Reptiles");
queue.Enqueue("Mammals");
queue.Enqueue("Fish");
queue.Enqueue("Birds");
// Display the elements
Console.WriteLine("Display the queue elements...");
foreach (string s in queue)
{
Console.WriteLine(s);
}
// Get the first element from the queue
Console.WriteLine("\n1st element = "+queue.Peek());
}
}
}
Output
Display the queue elements... Amphibians Reptiles Mammals Fish Birds 1st element = Amphibians
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