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Thread: Linked List problem, please help.

  1. #1
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    Lightbulb Linked List problem, please help.

    I am trying to make a method which receives the first list node of two different linked list's of ints and the method is supposed to insert the second list right before the smallest int of the first list. Here is what i have but it is very confusing and I do not know how to fix it. The other methods of the program are working fine.
    public static ListNode insertBeforeSmallest (ListNode headMain, ListNode headInsert)
        {
     
            ListNode start = headMain;
            ListNode prevNodeMain = headMain;
            ListNode prevNodeMain2 = headMain;
            ListNode nodePtrMain = headMain.getNext ();
            ListNode nodePtrMain2 = headMain.getNext ();
            ListNode nodePtrInsert = headInsert;
            int length = Length (prevNodeMain);
            String lowestObj = "";
            for (int j = 0 ; j < length ; j++)
            {
                if (j == 0)
                {
                    lowestObj = ((String)prevNodeMain.getValue ());
                    prevNodeMain = nodePtrMain;
                    nodePtrMain = nodePtrMain.getNext ();
                }
                else if (((String)prevNodeMain.getValue ()).compareTo (nodePtrMain.getValue ()) < 0)
                {
                    lowestObj = (String)nodePtrMain.getValue ();
                    prevNodeMain = nodePtrMain;
                    nodePtrMain = nodePtrMain.getNext ();
                }
                else
                {
                    prevNodeMain = nodePtrMain;
                    nodePtrMain = nodePtrMain.getNext ();
                }
            }
            while (nodePtrMain2 != null)
            {
                if(prevNodeMain2.getNext ().getValue ().equals (lowestObj))
     
                    {
                        prevNodeMain2.getNext ().setNext (nodePtrInsert);
                        for (int i = 0 ; i < (Length (nodePtrInsert) - 1) ; i++)
                        {
                            nodePtrInsert.setNext (nodePtrInsert.getNext ());
                        }
                        nodePtrInsert.setNext (nodePtrMain2);
                        return start;
                    }
                else
                {
                    prevNodeMain2 = nodePtrMain2;
                    nodePtrMain2 = nodePtrMain2.getNext ();
                }
            }
            return null;
     
        }
    Last edited by helloworld922; December 20th, 2010 at 12:01 PM.


  2. #2
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    Default Re: Linked List problem, please help.

    Hey Axeander,

    Just a small thing, please use

    code goes here
    while posting your java code.

    That would make the code more readable for us.

    We appreciate your co-operation.

    Goldest
    Java Is A Funny Language... Really!

    Sun: Java Coding Conventions

    Click on THANKS if you like the solution provided.
    Click on Star if you are really impressed with the solution.

  3. #3
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    Default Re: Linked List problem, please help.

    Ok thanks, but I'm cant find how to use that. Is it build into the post box, or do I need to get it from somewhere else?

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    Default Re: Linked List problem, please help.

    Quote Originally Posted by Axeander View Post
    Ok thanks, but I'm cant find how to use that. Is it build into the post box, or do I need to get it from somewhere else?
    Hi Axeander, you can get your code into the box by editing your post above and flanking the source code with either the [highlight=java][/highlight] or [code][/code], where the code goes between the bracketed tags.

  5. The Following User Says Thank You to copeg For This Useful Post:

    Axeander (December 21st, 2010)

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    Default Re: Linked List problem, please help.

    Ok thanks, but do you have any suggestions about the code its self? I really need some help on it.

  7. #6
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    Default Re: Linked List problem, please help.

    ListNode<Integer> start as your ListNode stores Integers.

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    Default Re: Linked List problem, please help.

    int length = Length (prevNodeMain);

    I don't see what this is for.

    Usually you look at the size of the entire list, not a just a single Node.

    Unless Length is another method in the class that you're not showing because you've already got it figured out.

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    Default Re: Linked List problem, please help.

    (String)prevNodeMain.getValue ()

    If you're using Integers,

    prevNodeMain.getValue().toString() would be better.

    I don't think the way you have it now will work.

  10. #9
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    Default Re: Linked List problem, please help.

    Also, the ListNodes you're passing as parameters should have their data types. I think that you said they were both Integer.

    public static ListNode<Integer> insertBeforeSmallest (ListNode<Integer> headMain, ListNode<Integer> headInsert)

  11. The Following User Says Thank You to javapenguin For This Useful Post:

    Axeander (December 21st, 2010)

  12. #10
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    Default Re: Linked List problem, please help.

    Yes I already have the method Length on the rest of the program which is working but for some reason when i run the program using this code,
     public static void main (String[] args)
        {
     
            ListNode startList, startInsert;
            System.out.println ("Entering the original list...");
            startList = getLinkedList ();
            System.out.println ("Entering the list to be inserted...");
            startInsert = getLinkedList ();
            startList = insertBeforeSmallest (startList, startInsert);
     
            // prints elements of a linked list
            ListNode tempNode = startList;
            while (tempNode != null)
            {
                System.out.println (tempNode.getValue ().toString ());
                tempNode = tempNode.getNext ();
            }
        } // main method
     
     
        public static ListNode getLinkedList ()
        { //gets linked list
            ListNode startNode, node, lastNode;
            System.out.println ("Type in a name,'none' to quit..");
            String name = Stdin.readLine ();
            if (name.equals ("none"))
                startNode = null;
            else
            {
                startNode = new ListNode (name, null);
                lastNode = startNode;
                do
                {
                    System.out.println ("Type in a name, 'none' to quit.");
                    name = Stdin.readLine ();
                    if (!name.equals ("none"))
                    {
                        node = new ListNode (name, null);
                        lastNode.setNext (node);
                        lastNode = node;
                    }
                }
                while (!name.equals ("none"));
            } //else
            return startNode;
        }

    I get stuck in the while loop "while(tempNode != null)" and keeps printing the same 2 number over and over.

  13. #11
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    Smile Re: Linked List problem, please help.

    Ok thanks everyone, I just finished it up. Thanks for the help.

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