排队。C# 中的 Peek 方法
原文:https://www.geeksforgeeks.org/queue-peek-method-in-c-sharp/
此方法返回队列开头的对象，而不移除它。此方法类似于出列方法，但 Peek 不修改队列，是一个 O(1)操作。该方法属于系统。集合命名空间。
语法:
public virtual object Peek ();
返回值:队列开头的对象。
异常:如果队列为空，此方法将给出无效操作异常。
以下程序说明了上述方法的使用:
例 1:
// C# code to illustrate the
// Queue.Peek Method
using System;
using System.Collections;
class GFG {
// Driver code
public static void Main()
{
// Creating a Queue
Queue myQueue = new Queue();
// Inserting the elements into the Queue
myQueue.Enqueue("1st Element");
myQueue.Enqueue("2nd Element");
myQueue.Enqueue("3rd Element");
myQueue.Enqueue("4th Element");
myQueue.Enqueue("5th Element");
myQueue.Enqueue("6th Element");
// Displaying the count of elements
// contained in the Queue
Console.Write("Total number of elements in the Queue are : ");
Console.WriteLine(myQueue.Count);
// Displaying the beginning element of Queue
// without removing it from the Queue
Console.WriteLine("Element at the beginning is : "
+ myQueue.Peek());
// Displaying the beginning element of Queue
// without removing it from the Queue
Console.WriteLine("Element at the beginning is : "
+ myQueue.Peek());
// Displaying the count of elements
// contained in the Queue
Console.Write("Total number of elements in the Queue are : ");
Console.WriteLine(myQueue.Count);
}
}
输出:
Total number of elements in the Queue are : 6
Element at the beginning is : 1st Element
Element at the beginning is : 1st Element
Total number of elements in the Queue are : 6
例 2:
// C# code to illustrate the
// Queue.Peek Method
using System;
using System.Collections;
class GFG {
// Driver code
public static void Main()
{
// Creating a Queue
Queue myQueue = new Queue();
// Displaying the beginning element of Queue
// without removing it from the Queue
// Calling Peek() method on empty Queue
// will throw InvalidOperationException.
Console.WriteLine("Element at the beginning is : "
+ myQueue.Peek());
}
}
运行时错误:
未处理异常: 系统。无效操作异常:队列为空。
参考:
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