Queue<T>.ToArray 方法
定义
重要
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将 Queue<T> 元素复制到新数组。
public:
cli::array <T> ^ ToArray();
public T[] ToArray ();
member this.ToArray : unit -> 'T[]
Public Function ToArray () As T()
返回
T[]
包含从 Queue<T> 复制的元素的新数组。
示例
下面的代码示例演示泛型类的 Queue<T> 多个方法,包括 ToArray 方法。
该代码示例创建具有默认容量的字符串队列, Enqueue 并使用 方法将五个字符串排队。 枚举队列的元素,这不会更改队列的状态。 方法 Dequeue 用于取消第一个字符串的排队。 方法 Peek 用于查看队列中的下一项,然后使用 Dequeue 方法取消排队。
ToArray方法用于创建数组并将队列元素复制到其中,然后将数组传递给Queue<T>采用 IEnumerable<T>的构造函数,创建队列的副本。 将显示副本的元素。
创建一个两倍于队列大小的数组,并使用 CopyTo 方法复制从数组中间开始的数组元素。 构造 Queue<T> 函数再次用于在开头创建队列的第二个副本,其中包含三个 null 元素。
方法 Contains 用于显示字符串“four”位于队列的第一个副本中,然后 Clear 该方法清除副本,属性 Count 显示队列为空。
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 first 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
*/
open System
open System.Collections.Generic
let numbers = Queue()
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 number in numbers do
printfn $"{number}"
printfn $"\nDequeuing '{numbers.Dequeue()}'"
printfn $"Peek at next item to dequeue: {numbers.Peek()}"
printfn $"Dequeuing '{numbers.Dequeue()}'"
// Create a copy of the queue, using the ToArray method and the
// constructor that accepts an IEnumerable<T>.
let queueCopy = numbers.ToArray() |> Queue
printfn $"\nContents of the first copy:"
for number in queueCopy do
printfn $"{number}"
// Create an array twice the size of the queue and copy the
// elements of the queue, starting at the middle of the
// array.
let array2 = numbers.Count * 2 |> Array.zeroCreate
numbers.CopyTo(array2, numbers.Count)
// Create a second queue, using the constructor that accepts an
// IEnumerable(Of T).
let queueCopy2 = Queue array2
printfn $"\nContents of the second copy, with duplicates and nulls:"
for number in queueCopy2 do
printfn $"{number}"
printfn $"""\nqueueCopy.Contains "four" = {queueCopy.Contains "four"}"""
printfn $"\nqueueCopy.Clear()"
queueCopy.Clear()
printfn $"queueCopy.Count = {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 first 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
注解
Queue<T>未修改 。 新数组中元素的顺序与元素从 开始 Queue<T> 到结束的顺序相同。
此方法是 O (n
) 操作,其中 n
为 Count。