Queue<T>.Enqueue(T) Método

Definição

Adiciona um objeto ao final do Queue<T>.Adds an object to the end of the Queue<T>.

public:
 void Enqueue(T item);
public void Enqueue (T item);
member this.Enqueue : 'T -> unit
Public Sub Enqueue (item As T)

Parâmetros

item
T

O objeto a ser adicionado ao Queue<T>.The object to add to the Queue<T>. O valor pode ser null para tipos de referência.The value can be null for reference types.

Exemplos

O exemplo de código a seguir demonstra vários métodos Queue<T> da classe genérica, incluindo Enqueue o método.The following code example demonstrates several methods of the Queue<T> generic class, including the Enqueue method.

O exemplo de código cria uma fila de cadeias de caracteres com capacidade Enqueue padrão e usa o método para enfileirar cinco cadeias de caracteres.The code example creates a queue of strings with default capacity and uses the Enqueue method to queue five strings. Os elementos da fila são enumerados, o que não altera o estado da fila.The elements of the queue are enumerated, which does not change the state of the queue. O Dequeue método é usado para remover a primeira cadeia de caracteres da fila.The Dequeue method is used to dequeue the first string. O Peek método é usado para examinar o próximo item na fila e, em seguida, o Dequeue método é usado para remover a fila.The Peek method is used to look at the next item in the queue, and then the Dequeue method is used to dequeue it.

O ToArray método é usado para criar uma matriz e copiar os elementos de fila para ela, então a matriz é passada para Queue<T> o construtor que IEnumerable<T>usa, criando uma cópia da fila.The ToArray method is used to create an array and copy the queue elements to it, then the array is passed to the Queue<T> constructor that takes IEnumerable<T>, creating a copy of the queue. Os elementos da cópia são exibidos.The elements of the copy are displayed.

Uma matriz duas vezes o tamanho da fila é criado e o CopyTo método é usado para copiar os elementos da matriz que começam no meio da matriz.An array twice the size of the queue is created, and the CopyTo method is used to copy the array elements beginning at the middle of the array. O Queue<T> Construtor é usado novamente para criar uma segunda cópia da fila que contém três elementos nulos no início.The Queue<T> constructor is used again to create a second copy of the queue containing three null elements at the beginning.

O Contains método é usado para mostrar que a cadeia de caracteres "quatro" está na primeira cópia da fila, após a qual Clear o método limpa a cópia e a Count Propriedade mostra que a fila está vazia.The Contains method is used to show that the string "four" is in the first copy of the queue, after which the Clear method clears the copy and the Count property shows that the queue is empty.

using System;
using System.Collections.Generic;

class Example
{
    public static void Main()
    {
        Queue<string> numbers = new Queue<string>();
        numbers.Enqueue("one");
        numbers.Enqueue("two");
        numbers.Enqueue("three");
        numbers.Enqueue("four");
        numbers.Enqueue("five");

        // A queue can be enumerated without disturbing its contents.
        foreach( string number in numbers )
        {
            Console.WriteLine(number);
        }

        Console.WriteLine("\nDequeuing '{0}'", numbers.Dequeue());
        Console.WriteLine("Peek at next item to dequeue: {0}", 
            numbers.Peek());
        Console.WriteLine("Dequeuing '{0}'", numbers.Dequeue());

        // Create a copy of the queue, using the ToArray method and the
        // constructor that accepts an IEnumerable<T>.
        Queue<string> queueCopy = new Queue<string>(numbers.ToArray());

        Console.WriteLine("\nContents of the first copy:");
        foreach( string number in queueCopy )
        {
            Console.WriteLine(number);
        }
        
        // Create an array twice the size of the queue and copy the
        // elements of the queue, starting at the middle of the 
        // array. 
        string[] array2 = new string[numbers.Count * 2];
        numbers.CopyTo(array2, numbers.Count);
        
        // Create a second queue, using the constructor that accepts an
        // IEnumerable(Of T).
        Queue<string> queueCopy2 = new Queue<string>(array2);

        Console.WriteLine("\nContents of the second copy, with duplicates and nulls:");
        foreach( string number in queueCopy2 )
        {
            Console.WriteLine(number);
        }

        Console.WriteLine("\nqueueCopy.Contains(\"four\") = {0}", 
            queueCopy.Contains("four"));

        Console.WriteLine("\nqueueCopy.Clear()");
        queueCopy.Clear();
        Console.WriteLine("\nqueueCopy.Count = {0}", queueCopy.Count);
    }
}

/* This code example produces the following output:

one
two
three
four
five

Dequeuing 'one'
Peek at next item to dequeue: two
Dequeuing 'two'

Contents of the copy:
three
four
five

Contents of the second copy, with duplicates and nulls:



three
four
five

queueCopy.Contains("four") = True

queueCopy.Clear()

queueCopy.Count = 0
 */
Imports System.Collections.Generic

Module Example

    Sub Main

        Dim numbers As New Queue(Of String)
        numbers.Enqueue("one")
        numbers.Enqueue("two")
        numbers.Enqueue("three")
        numbers.Enqueue("four")
        numbers.Enqueue("five")

        ' A queue can be enumerated without disturbing its contents.
        For Each number As String In numbers
            Console.WriteLine(number)
        Next

        Console.WriteLine(vbLf & "Dequeuing '{0}'", numbers.Dequeue())
        Console.WriteLine("Peek at next item to dequeue: {0}", _
            numbers.Peek())    
        Console.WriteLine("Dequeuing '{0}'", numbers.Dequeue())

        ' Create a copy of the queue, using the ToArray method and the
        ' constructor that accepts an IEnumerable(Of T).
        Dim queueCopy As New Queue(Of String)(numbers.ToArray())

        Console.WriteLine(vbLf & "Contents of the first copy:")
        For Each number As String In queueCopy
            Console.WriteLine(number)
        Next
        
        ' Create an array twice the size of the queue, compensating
        ' for the fact that Visual Basic allocates an extra array 
        ' element. Copy the elements of the queue, starting at the
        ' middle of the array. 
        Dim array2((numbers.Count * 2) - 1) As String
        numbers.CopyTo(array2, numbers.Count)
        
        ' Create a second queue, using the constructor that accepts an
        ' IEnumerable(Of T).
        Dim queueCopy2 As New Queue(Of String)(array2)

        Console.WriteLine(vbLf & _
            "Contents of the second copy, with duplicates and nulls:")
        For Each number As String In queueCopy2
            Console.WriteLine(number)
        Next

        Console.WriteLine(vbLf & "queueCopy.Contains(""four"") = {0}", _
            queueCopy.Contains("four"))

        Console.WriteLine(vbLf & "queueCopy.Clear()")
        queueCopy.Clear()
        Console.WriteLine(vbLf & "queueCopy.Count = {0}", _
            queueCopy.Count)
    End Sub
End Module

' This code example produces the following output:
'
'one
'two
'three
'four
'five
'
'Dequeuing 'one'
'Peek at next item to dequeue: two
'
'Dequeuing 'two'
'
'Contents of the copy:
'three
'four
'five
'
'Contents of the second copy, with duplicates and nulls:
'
'
'
'three
'four
'five
'
'queueCopy.Contains("four") = True
'
'queueCopy.Clear()
'
'queueCopy.Count = 0

Comentários

Se Count já for igual à capacidade, a capacidade Queue<T> do será aumentada realocando automaticamente a matriz interna e os elementos existentes serão copiados para a nova matriz antes que o novo elemento seja adicionado.If Count already equals the capacity, the capacity of the Queue<T> is increased by automatically reallocating the internal array, and the existing elements are copied to the new array before the new element is added.

Se Count for menor que a capacidade da matriz interna, esse método será uma operação O (1).If Count is less than the capacity of the internal array, this method is an O(1) operation. Se a matriz interna precisar ser realocada para acomodar o novo elemento, esse método se tornará umanoperação O () n , Countem que é.If the internal array needs to be reallocated to accommodate the new element, this method becomes an O(n) operation, where n is Count.

Aplica-se a

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