Queue<T>.Contains(T) Método

Definición

Determina si un elemento se encuentra en Queue<T>.Determines whether an element is in the Queue<T>.

public:
 bool Contains(T item);
public bool Contains (T item);
member this.Contains : 'T -> bool
Public Function Contains (item As T) As Boolean

Parámetros

item
T

Objeto que se va a buscar en Queue<T>.The object to locate in the Queue<T>. El valor puede ser null para los tipos de referencia.The value can be null for reference types.

Devoluciones

true si item se encuentra en la matriz Queue<T>; en caso contrario, false.true if item is found in the Queue<T>; otherwise, false.

Ejemplos

En el ejemplo de código siguiente se muestran varios métodos de la clase genérica Queue<T>, incluido el método Contains.The following code example demonstrates several methods of the Queue<T> generic class, including the Contains method.

En el ejemplo de código se crea una cola de cadenas con la capacidad predeterminada y se usa el método Enqueue para poner en cola cinco cadenas.The code example creates a queue of strings with default capacity and uses the Enqueue method to queue five strings. Los elementos de la cola se enumeran, lo que no cambia el estado de la cola.The elements of the queue are enumerated, which does not change the state of the queue. El método Dequeue se usa para quitar la cola de la primera cadena.The Dequeue method is used to dequeue the first string. El método Peek se utiliza para examinar el siguiente elemento de la cola y, a continuación, se usa el método Dequeue para quitar de la cola.The Peek method is used to look at the next item in the queue, and then the Dequeue method is used to dequeue it.

El método ToArray se usa para crear una matriz y copiar los elementos de la cola en ella, a continuación, la matriz se pasa al constructor Queue<T> que toma IEnumerable<T>y crea una copia de la cola.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. Se muestran los elementos de la copia.The elements of the copy are displayed.

Se crea una matriz dos veces el tamaño de la cola y se usa el método CopyTo para copiar los elementos de la matriz a partir de la parte central de la 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. El constructor de Queue<T> se utiliza de nuevo para crear una segunda copia de la cola que contiene tres elementos nulos al principio.The Queue<T> constructor is used again to create a second copy of the queue containing three null elements at the beginning.

El método Contains se usa para mostrar que la cadena "cuatro" se encuentra en la primera copia de la cola, después de la cual el método Clear borra la copia y la propiedad Count muestra que la cola está vacía.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

Comentarios

Este método determina la igualdad mediante el comparador de igualdad predeterminado EqualityComparer<T>.Default para T, el tipo de valores de la cola.This method determines equality using the default equality comparer EqualityComparer<T>.Default for T, the type of values in the queue.

Este método realiza una búsqueda lineal; por lo tanto, este método es una operación O (n), donde se Countn.This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.

Se aplica a

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