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Thread: please teach me how to do this Link List assignment

  1. #1
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    Default please teach me how to do this Link List assignment

    please teach me to do this assignment question no7,just question no 7 because i really dont understand *public*void*
    swapMiddle() in Linked ListCapture.JPG
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  2. #2
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    Default Re: please teach me how to do this Link List assignment

    Swapping two elements of linked list requires changing the current pointers to the way they'd be if the items were swapped. In the original:

    1 -> 2
    2 -> 3
    3 -> 4

    Becomes

    1 -> 3
    3 -> 2
    2 -> 4

    Given two elements of a linked list, write a method to swap them by changing the pointers.

    But what's that got to do with "*public*void*?" 'public' is the access modifier and 'void' is the return type. What don't you understand about those?

  3. #3
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    Default Re: please teach me how to do this Link List assignment

    so we need create method in link list class?

  4. #4
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    Default im trying to do this LinkList method but still not work

    can somebody help me fix this code as i want to swap the middle number
     
    public class LinkList
    {
        private Node first;
        private Node last;
        private Node current;
     
        public LinkList()
        {
            first = null;
            last = null;
            current = null;
        }
     
        public void insertAtBack(Object insertitem)
        {
            Node newNode = new Node(insertitem);
     
            if(isEmpty())
            {
                first = newNode;
                last = newNode;
            }
            else
            {
                last.next = newNode;
                last = newNode;
            }
        }
     
        public void insertAtFront(Object insertitem)
        {
            Node newNode = new Node(insertitem);
     
            if(isEmpty())
            {
                first = newNode;
                last = newNode;
            }
            else
            {
                newNode.next=first;
                first=newNode;
            }
        }
     
        public Object getFirst()
        {
            if(isEmpty())
            {
                return null;
            }
            else
            {
                current = first;
                return current.data;
            }
        }
     
        public Object getNext()
        {
            if(current ==last)
            {
                return null;
            }
            else
            {
                current = current.next;
                return current.data;
            }
        }
     
        public Object removeFromFront()
        {
            Object removeItem=null;
            if(isEmpty())
            {
                return removeItem;
            }
            removeItem = first.data;
            if(first==last)
            {
                first=null;
                last=null;
            }
            else
            {
                first=first.next;
            }
            return removeItem;
        }
     
        public Object removeFromBack()
        {
            Object removeItem=null;
            if(isEmpty())
            {
                return removeItem;
            }
            removeItem=last.data;
            if(first==last)
            {
                first=null;
                last=null;
            }
            else
            {
                current=first;
                while(current.next!=last)
                {
                    current=current.next;
                }
                last=current;
                last.next=null;
            }
            return removeItem;
        }
     
        public boolean isEmpty()
        {
            return(first==null);
     
        }
     
        public void swapMiddle(Object obj)
        {
            Node tmp =new Node(obj) ;
            first = last;
            last = tmp;
        }
     
       //this is LinkList class 
     
    }
     
    import javax.swing.*;
     
    public class swap
    {
        public static void main(String[]args)
        {
            LinkList swapM=new LinkList();
     
            for(int i=1;i<=4;i++)
            swapM.insertAtBack(i);
            System.out.println("Sequence of data BEFORE insertion:");
            Object obj=swapM.getFirst();
            while(obj!=null)
            {
                System.out.println(obj);
                obj=swapM.getNext();
            }
     
            swapM.swapMiddle(obj);
     
            System.out.println("Sequence of data AFTER insertion:");
            obj=swapM.getFirst();
            while(obj!=null)
            {
                System.out.println(obj);
                obj=swapM.getNext();
            }
        }
    }

  5. #5
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    Default can somebody fix my coding?

    can somebody help me fix this code as i want to swap the middle number
     
    public class LinkList
    {
        private Node first;
        private Node last;
        private Node current;
     
        public LinkList()
        {
            first = null;
            last = null;
            current = null;
        }
     
        public void insertAtBack(Object insertitem)
        {
            Node newNode = new Node(insertitem);
     
            if(isEmpty())
            {
                first = newNode;
                last = newNode;
            }
            else
            {
                last.next = newNode;
                last = newNode;
            }
        }
     
        public void insertAtFront(Object insertitem)
        {
            Node newNode = new Node(insertitem);
     
            if(isEmpty())
            {
                first = newNode;
                last = newNode;
            }
            else
            {
                newNode.next=first;
                first=newNode;
            }
        }
     
        public Object getFirst()
        {
            if(isEmpty())
            {
                return null;
            }
            else
            {
                current = first;
                return current.data;
            }
        }
     
        public Object getNext()
        {
            if(current ==last)
            {
                return null;
            }
            else
            {
                current = current.next;
                return current.data;
            }
        }
     
        public Object removeFromFront()
        {
            Object removeItem=null;
            if(isEmpty())
            {
                return removeItem;
            }
            removeItem = first.data;
            if(first==last)
            {
                first=null;
                last=null;
            }
            else
            {
                first=first.next;
            }
            return removeItem;
        }
     
        public Object removeFromBack()
        {
            Object removeItem=null;
            if(isEmpty())
            {
                return removeItem;
            }
            removeItem=last.data;
            if(first==last)
            {
                first=null;
                last=null;
            }
            else
            {
                current=first;
                while(current.next!=last)
                {
                    current=current.next;
                }
                last=current;
                last.next=null;
            }
            return removeItem;
        }
     
        public boolean isEmpty()
        {
            return(first==null);
     
        }
     
        public void swapMiddle(Object obj)
        {
            Node tmp =new Node(obj) ;
            first = last;
            last = tmp;
        }
     
       //this is LinkList class 
     
    }
     
    import javax.swing.*;
     
    public class swap
    {
        public static void main(String[]args)
        {
            LinkList swapM=new LinkList();
     
            for(int i=1;i<=4;i++)
            swapM.insertAtBack(i);
            System.out.println("Sequence of data BEFORE insertion:");
            Object obj=swapM.getFirst();
            while(obj!=null)
            {
                System.out.println(obj);
                obj=swapM.getNext();
            }
     
            swapM.swapMiddle(obj);
     
            System.out.println("Sequence of data AFTER insertion:");
            obj=swapM.getFirst();
            while(obj!=null)
            {
                System.out.println(obj);
                obj=swapM.getNext();
            }
        }
    }

  6. #6
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    Default Re: please teach me how to do this Link List assignment

    Please don't start multiple threads on the same topic.

    What help do you need with the code you posted? Are there errors? If so, post them. Does the swap not work as intended? If so, describe what is happening and what should be happening. Ask specific questions about what you need help with.

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