尝试将链表转换为循环链表

Question

我一直在做这项任务很长一段时间。我终于让测试人员打印列表中的内容和方法工作，但现在我需要连接列表上的元素形成一个圆圈，并在删除或添加元素时保持这种方式。我的书没有涵盖有关循环链表的任何内容，我试图将我在这里看到的一些样本的概念应用于循环链表而没有任何成功。

我非常感谢任何帮助。

这就是我所拥有的：

import java.util.NoSuchElementException;

/**
A circular linked list.
 */
public class LinkedList
{  
    private Node last;
    // Don't add other instance fields
    /** 
    Constructs an empty linked list.
     */
    public LinkedList()
    {  
        last = null;
    }

    /**
    Returns the first element in the linked list.
    @return the first element in the linked list
     */
    public Object getFirst()
    {  
        //. . .
        if (last == null) 
            throw new NoSuchElementException();
        return last.data;
    }

    /**
    Removes the first element in the linked list.
    @return the removed element
     */
    public Object removeFirst()
    {  
        //. . .
        if (last == null)
            throw new NoSuchElementException();
        Object element = last.data;
        last = last.next;
        return element;
    }

    /**
    Adds an element to the front of the linked list.
    @param element the element to add
     */
    public void addFirst(Object element)
    {  
        //. . .
        Node newNode = new Node();
        newNode.data = element;
        newNode.next = last;
        last = newNode;
    }

    /**
    Adds an element to the end of the linked list.
    @param element the element to add
     */
    public void add(Object element)
    {  
        //. . .
        if (last == null)
        {
            addFirst(element);
            //position = last;//had to comment out
        }
        else
        {
            Node newNode = new Node();
            newNode.data = element;
            newNode.next = last.next;
            last.next = newNode;
            last = newNode;
        }
    }

    /**
    Returns an iterator for iterating through this list.
    @return an iterator for iterating through this list
     */
    public ListIterator listIterator()
    {  
        return new LinkedListIterator();
    }

    private class Node
    {  
        public Object data;
        public Node next;
    }

    private class LinkedListIterator implements ListIterator
    {              
        private Node position; 
        private Node previous; 

        /**
        Constructs an iterator that points to the front
        of the linked list.
         */
        public LinkedListIterator()
        {  
            position = null; 
            previous = null;
        }

        /**
        Moves the iterator past the next element.
        @return the traversed element
         */
        public Object next()
        {  
            //. . .
            if (!hasNext())
                throw new NoSuchElementException();
            previous = position; //remeber for remove

            if (position == null)
                position = last;
            else
                position = position.next;

            return position.data; //correct line
        }

        /**
        Tests if there is an element after the iterator 
        position.
        @return true if there is an element after the iterator 
        position
         */
        public boolean hasNext()
        {  
            //. . .
            if (position == null)
                return last != null;
            else 
                return position.next !=null;
        }

        /**
        Adds an element before the iterator position
        and moves the iterator past the inserted element.
        @param element the element to add
         */
        public void add(Object element)
        {  
            //. . .
            if (position == null)
            {
                addFirst(element);
                position = last;
            }
        }

        /**
        Removes the last traversed element. This method may
        only be called after a call to the next() method.
         */
        public void remove()
        {  
            //. . .
            if (previous == position)
                throw new IllegalStateException();
            if (position == last)
            {
                removeFirst();
            }
            else
            {
                previous.next = position.next;
            }
            position = previous;
        }

        /**
        Sets the last traversed element to a different 
        value. 
        @param element the element to set
         */
        public void set(Object element)
        {
            if (position == null)
                throw new NoSuchElementException();
            position.data = element;
        }

    }
}

Answer 1

下面的代码将帮助您创建循环链接列表

class CircularLinkedList
{
    class Node
    {
        int data;
        Node next, prev;

        public Node(int data)
        {
            this.data = data;
        }
    }

    private Node head;
    private int count;

    public Node getHead()
    {
        return head;
    }

    public int getCount()
    {
        return count;
    }

    public boolean isEmpty()
    {
        return head==null;
    }

    // Add new node after the "head"
    public void add(int data)
    {
        Node n = new Node(data);
        if(isEmpty())
        {
            head = n;
            n.next = head;
            n.prev = head;
        }
        else
        {
            n.next = head.next;
            n.prev = head;
            head.next = n;
            n.next.prev = n;
        }
        count++;
    }

    // Remove the node pointed by "head"
    public void remove()
    {
        if(isEmpty())
            return;

        if(count==1)
            head = null;
        else 
        {
            Node tmp = head;
            tmp.prev.next = tmp.next;
            tmp.next.prev = tmp.prev;
            head = head.next;
            tmp.next = tmp.prev = null;
        }
        count--;
    }

    public void print()
    {
        Node tmp = head.next;
        while(tmp!=head)
        {
            System.out.println(tmp.data+" ");
            tmp = tmp.next;
        }
    }
}

上面的代码将让您了解如何创建循环链表，添加，打印和删除节点 注意：因为这是您的作业所以我没有向您提供确切的代码。您可以使用它，并以您需要的方式理解和调整它。通过这个你可以很好地了解循环链接列表

如果您有任何问题。问我们。所以总是欢迎你:)）