C#队列显示实现-在不修改节点的情况下打印内容

Question

所以我的代码在链表版本中实现了Queue。一切正常，但显示方法。我花了好几天的时间试图找出在不修改节点或队列本身的情况下显示队列中节点内容的正确方法。

这是我的代码：

public class QueueNode
{        
private Object bike;
private QueueNode next;
public QueueNode(Object bike)
{
this.bike = bike;
next = null;            
}
public Object Bike //Content
{
get
{
return bike;
}
set
{
bike = value;
}
}
public QueueNode Next //Pointer
{
get
{
return next;
}
set
{
next = value;
}
}

}  // end of QueueNode
// This class inherits the interface IQueue, that uses these methods, not relevant here. 
public class CircularQueue : IQueue 
{
private int capacity = Int32.MaxValue;
private int count = 0;
private QueueNode tail = null; //Node
public int Capacity
{
get
{
return capacity;
}
}
public int Count
{
get
{
return count;
}
}
public bool IsEmpty()
{
return count == 0;
}

public bool IsFull()
{
return count == capacity;
}
public void Enqueue(Object item)
{
// check the pre-condition
if (!IsFull())
{
QueueNode aNode = new QueueNode(item);
if (count == 0) //special case: the queue is empty
{
tail = aNode;
tail.Next = tail;
}
else //general case
{
aNode.Next = tail.Next;
tail.Next = aNode;
tail = aNode;
}
count++;
}
}
public Object Dequeue()
{
// check the pre-condition
if (!IsEmpty())
{
Object data;
if (count == 1) //special case: the queue has only 1 item
{
data = tail.Bike;
tail = null;
}
else //general case
{
data = tail.Next.Bike;
tail.Next = tail.Next.Next;
}
count--;
return data;
}
else
return null;
}

我的问题：我创建此代码是为了显示节点的内容(它会显示所有节点(，但它最终会修改内容，在任务结束时在每个节点中放置相同的值。

/*public void DisplayBikes()
{
if (!IsEmpty())
{
Object data;
for(int i = 0; i <count; i++)
{
data = tail.Next.Bike;
Console.WriteLine(data);                    
tail.Next = tail.Next.Next;
}                
}
else
Console.WriteLine("Sorry. There are no Bikes available");
}*/

然后我有点冒险，创建了一个临时节点来显示队列中所有节点的内容，但最终却搞砸了。我收到这个消息：

System.NullReferenceException："对象引用未设置为对象的实例。">

tail为空

所以，在这一点上，我对如何做到这一点一无所知。我知道我已经很接近了，但我不知道我在这里缺少了什么，让这个代码打印我的节点的内容。。。。请帮忙！

public void DisplayBikes()
{
int c = count;
QueueNode temp = tail.Next;
if(!isFull())
{
while(c > 0)
{                
Console.WriteLine(temp.Bike);
temp = tail.Next.Next;
c--;
}
}
else
Console.WriteLine("Sorry. There are no Bikes available");
}

Answer 1

我自己解决了。

public void DisplayBikes()
{
int c = count;
QueueNode temp = tail.Next;
if(!isFull())
{
while(c > 0)
{                
Console.WriteLine(temp.Bike);
temp = temp.Next; //Here. I needed to iterate over the same node
c--;
}
}
else
Console.WriteLine("Sorry. There are no Bikes available");
}

就是这样。没有人敢帮忙。。。。所以，谢谢大家>：(