Question

我正在尝试使用单个引用实现循环链接列表队列。我相信它是基于测试的FIFO（后面是每次元素入队时都应该更新），但它是反向打印。我应该期待这个，还是我错过了什么？我试过更改toString（）。这是我的CircularLinkedQueue类：

public class CircularLinkedQueue implements UnboundedQueueInterface

{

protected LLObjectNode rear;        

public CircularLinkedQueue()
{
    rear = null;
}


public void enqueue(Object element)
{
    LLObjectNode newNode = new LLObjectNode(element);

    if (rear == null)
        newNode.setLink(newNode);

    newNode.setLink(rear);      
    rear = newNode;     
}// end enqueue()


public Object dequeue() throws QueueUnderflowException
{
    if (isEmpty())
        throw new QueueUnderflowException("Dequeue attempted on an empty queue.");
    else
    {
        Object element;                 // create a reference to the Object to return
        element = rear.getLink();       // set the reference to the information in the front node
        rear = rear.getLink();          // set the rear reference to point at the next node

        return element;                 
    }// end else
}// end dequeue()


public boolean isEmpty()
{
    return (rear == null);              
}// end isEmpty()


// *** Exercise #25b        *** works
public Object front()
// returns a reference to the front element on the queue.
// precondition: queue is not empty.
{
    Object frontObj;
    frontObj = rear.getLink();  
    return frontObj;
}// end front()


public int size()
{
    LLObjectNode node;
    node = rear;
    int count = 0;

    while (node != null)
    {
        count++;
        node = node.getLink();
    }
    return count;
}// end size()


public String toString()
{
    String circleQStr = "";
    LLObjectNode node;
    int count = 0;
    node = rear;

    while (node != null)
    {
        count++;
        circleQStr = circleQStr + count + ". " + node.getInfo() + "\n";
        node = node.getLink();
    }// end while
    return circleQStr;
    }// end toString()  
}// end class CircularLinkedQueue

以下是getLink()和setLink()：

    public void setLink(LLObjectNode link)
{
    // sets link of this LLObjectNode
    this.link = link;
}


public LLObjectNode getLink()
{
    // returns link of this LLObjectNode
    return link;
}

感谢您阅读我的帖子。

Answer 1

此代码存在许多问题，我认为这与您说明的问题无关，但如果您的起始节点位于后方，则需要在打印之前前进，否则它将首先打印后部。另外......我认为你的size()函数不会返回...在循环队列中，下一个元素永远不会为空。如果没有发布getLink()和setLink()

的代码，也很难对其进行调试

修改好吧，我认为问题是你的enequeue方法应该是这样的

public void enqueue(Object element)
{
    LLObjectNode newNode = new LLObjectNode(element);

    if (rear == null){
        newNode.setLink(newNode);

    }else{
        newNode.setLink(rear.getLink()); 
        rear.setLink(newNode);      
    } 

    rear = newNode;   
}// end enqueue()

此外，您需要更改出队方法。现在你的后部指向你刚刚出局的元素。

public Object dequeue() throws QueueUnderflowException
{
    if (isEmpty())
        throw new QueueUnderflowException("Dequeue attempted on an empty queue.");
    else
    {
        Object element;                 // create a reference to the Object to return
        element = rear.getLink();       // set the reference to the information in the front node
        rear.setLink(element.getLink());          // set the rear reference to point at the next node

        return element;                 
    }// end else
}// end dequeue()

我应该期望循环链表列表向后打印吗？

1 个答案: