Linked List - insert between certain numbers

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  • July Lee
    New Member
    • Oct 2011
    • 1
    #1

    Linked List - insert between certain numbers

    I need to insert a new int into a list of its. BUT - It needs to be after a number smaller than it, and before a number larger than it, but the list is not to be sorted. It's driving me bonkers. I have 3 classes - all work right except for these assignments in my List class:
    if (current.getNex t() < temp && current > temp)
    while (current.getNex t() == index)

    I am very good at rookie errors - please help if you can...
    Code:
    public class List extends ListNode
{
	public ListNode head;
	public int listCount;
	
	//constructor
	public List()
	{
		head = null;
		listCount=0;
	}
	
	//to append the list
	public void appendItem(int item)
	{
		ListNode newNode = new ListNode(item);
		
		if (head == null)		
		{
			head = newNode;
		}
		else					
		{
			// find last item in list
			ListNode nextNode = head;
			
			while (nextNode.getNext() != null)
			{
				nextNode = nextNode.getNext();
			}
			
			nextNode.setNext(newNode);
		}
	}
	
	
	//to insert item at a certain point
	public void insertItem(int item, int index)
	{
		ListNode temp = new ListNode(item);
		ListNode current = head;
		
		while (current.getNext()!= null )
			for(int i = 1; i < index && current.getNext() != null; i++)
			{
				if (current.getNext() < temp && current > temp)
				{
				current = current.getNext();
				}
			}
		
		temp.setNext(current.getNext());
		current.setNext(temp);
		listCount++;
	}

	// to delete a specific item
	public boolean deleteItem(int index)
	{
		ListNode current = head;
		if (head == null)
		{
			return false;
		}
		while (current.getNext() == index)
		{
			if(current.getNext() == null)
				return false;
			current = current.getNext();
		}
		current.setNext(current.getNext());
		
		return true;
	}

	// to print the list
	public void printItem()
	{ 
		ListNode nextNode = head;
		
		while (nextNode!= null)
		{
			System.out.print(nextNode.getNext());
		}
	}
	
		
	public ListNode getHead()
	{
		return head;
	}

}
    Code:
    public class ListNode 
{
	private int newItem;
	private ListNode nextNode;
	
	
	public ListNode()
	{
		newItem = 0;
		nextNode = null;
	}
	
	public ListNode(int item)
	{
		newItem = item;
		nextNode = null;
	}
	
	public void setNext(ListNode next)
	{
		nextNode = next;
	}
	
	public ListNode getNext()
	{
		return nextNode;
	}
	
	public void setItem(int item)
	{
		newItem = item;
	}
	
	public int getItem()
	{
		return newItem;
	}
}
    Code:
    public class LinkedListDriver extends List 

{

       public static void main(String[] args) 

       {

              List list = new List();

       

              list.appendItem(1);

              list.appendItem(2);

              list.appendItem(3);

              list.appendItem(42);

              list.appendItem(5);

              list.appendItem(2);

              

              list.insertItem(0);

              list.insertItem(5);

 

              list.insertItem(4);

              list.insertItem(192);

              list.appendItem(9);

              

              list.insertItem(3);

              list.appendItem(3);

              

              System.out.println("Print after insert and appends");

              list.printItem();

              

              //list.deleteItem(9);

              //list.deleteItem(1);

                           

              //list.deleteItem(3);

 

              System.out.println("Print after deletes");

              list.printItem();

 

              list.appendItem(44);

              list.appendItem(22);

              list.appendItem(1);

              

              System.out.println("Print prior to sort");

              list.printItem();

              

              //list.sort();

              

              System.out.println("Print after sort");

              list.printItem();

       }
}
    Tags: None
    • isprabu
      New Member
      • Oct 2011
      • 1
      #2
      Modified List class

      Your List class needs few modifications. I have made the changes in append, insert, delete and print methods. Now the list handles all those basic operations properly.

      Your other point "BUT - It needs to be after a number smaller than it, and before a number larger than it" is not clear to me. If you explain it in detail (with example), i can try to help you in that regard too.
      Hope this helps!

      Code:
      public class List extends ListNode {
	    public ListNode head;
	    public int listCount;
	 
	    //constructor
	    public List()
	    {
	        head = null;
	        listCount=0;
	    }
	 
	    //to append the list
	    public void appendItem(int item)
	    {
	        ListNode newNode = new ListNode(item);
	 
	        if (head == null)        
	        {
	            head = newNode;
	        }
	        else                    
	        {
	            // find last item in list
	            ListNode nextNode = head;
	 
	            while (nextNode.getNext() != null)
	            {
	                nextNode = nextNode.getNext();
	            }
	 
	            nextNode.setNext(newNode);
	        }
	        listCount++; // this is required!
	    }
	 
	 
	    //to insert item at a certain point
	    public void insertItem(int item, int index)
	    {
	        ListNode temp = new ListNode(item);
	        ListNode current = head;
	
	        if (index < 0 || index > listCount) return; // error
	        if (index == 0) {
	        	// replace 'head' position
	        	temp.setNext(head);
	        	head = temp;	        	
	        } else {
	            for(int i = 1; i < index && current.getNext() != null; i++)
	            {
	                //if (current.getNext().getItem() < temp.getItem() && current.getItem() > temp.getItem())
	                //{
	                //current = current.getNext();
	                //}
	                current = current.getNext();
	            }
		 
		        temp.setNext(current.getNext());
		        current.setNext(temp);
	        }
	        listCount++;
	    }
	 
	    // to delete a specific item
	    public boolean deleteItem(int index)
	    {
	        ListNode current = head;
	        ListNode prev = null;
	        int i = 0; 
	        while (current != null) 
	        {
	        	if (i == index) { 
	        		// matching location found
	        		if (prev != null) {
	        			prev.setNext(current.getNext());
	        		} else {
	        			// this means we are deleting the 'head' item
	        			head = current.getNext();
	        		}
	        		listCount--;
	        		return true;
	        	}
	        	prev = current;
	        	current = current.getNext();
	        	i++;
	        }
	        return false;
	    }
	 
	    // to print the list
	    public void printItem()
	    { 
	        ListNode nextNode = head;
	 
	        while (nextNode!= null)
	        {
	        	System.out.println(nextNode.getItem()); 
	            nextNode = nextNode.getNext(); 
	        }
	    }
}

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