[Meemozeezo1]

I'm taking Data Structure & Algorithms subject and don't have any background. I saw the following exercise and don't know how to implement it in Java although I have already taken Java. Can anyone help.

For each of the following task:
Display all the integers in an array of integers.
Display all integers in a chain of linked nodes.
Display the nth integer in an array of integers.
Compute the sum of the first n even integers in an array of integers.
i. Write a program fragment using Java.
ii. Indicate the time requirement using big-Oh notation in the worst case

[UnrealEd]

Have a look at the LinkedList class, or if you're not familiar with the concept of linked lists, Wikipedia - Linked List.

The integer in array part should be doable if you have programmed in Java before. That's pretty straightforward. There are 2 options: you either loop over the array, or you use a recursive function.

I wasn't that good in calculating execution times in big O notation, so I can't really help you with that. Have a look around the web, cause I'm sure you'll find some decent info on that topic

[Meemozeezo1]

Thanks for your help. I have a problem with this code, if you can pin point to the error that I'm having, I'd appreciate it:

Code:

/* Node.java             Authors: Koffman & Wolz
 * Represents a node with information and link fields.
 */
class Node 
{   
   // Data fields for Node   
   private Object info;       // data stored in the node
   private Node link;         // link to next node

   // Methods
   // Constructors
   // postcondition: Creates a new empty node.
   public Node() {
     info = null;
     link = null;
   }

   // postcondition: Creates a new node storing obj.
   public Node(Object obj) {
     info = obj;
     link = null;
   }

   // postcondition: Creates a new node storing obj 
   //   and linked to node referenced by next.
   public Node(Object obj, Node next) {
     info = obj;
     link = next;
   } 

   // accessors

   public Object getInfo() 
   {
      return info;
   }

   public Object getLink() 
   {
      return link;
   }


   // mutators
   public void setInfo(Object newInfo) 
   {
      info = newInfo;
   }

   public void setLink(Node newLink) 
   {
      link = newLink;
   }
} 
//////////////////////////////////////////
public class LinkedList {
		Node head,tail,current;		

public LinkedList() {
    }
      
//For (Initially Nodes contains = 0,3,5,7) you can use this method inside class Linked List.

public void initial( )
{
	Node newNode = new Node(new Integer(0));
	head = newNode();
	Node newNode = new Node(new Integer(3));
	head = newNode( );
	newNode.setLink(head);
	newNode = new Node(new Integer(5));
	newNode.setLink(head);
	head = newNode( );
	newNode = new Node(new Integer(7));
	newNode.setLink(head);
	head = newNode( );
}
//the methods to be used here are:
public void insertLast(int i) 				//insert at last of list
{
	Node newNode= new Node(i);			 	//makes new LinkedList
	if (head == null)
		head = newNode;						
	else
	{
	if (head.getLink() ==null) 						//head.link==null
	head.setLink (newNode);							//head.link = newNode
	else
	{
		Node current = head;
		//traversing nodes
	while (current.getLink() !=null)			//current.link !=null
	current = current.getLink();				//current = current.link
	current.setLink (newNode);					//current.link= newNode
	}
	}
//.....................................................................
 public void deleteByTarget(int source, int target)					//deletes by target
{
if (head == null)
  System.out.println("Cannot delete data");
else if (head.getInfo() == target)
   head = head.getLink();
else
{
   Node before = null;
   Node current= head;

  // current.info != target
   while ( (current.getInfo() != target) && (current != null) )
   {
      before = current;
      current = current.getLink(); // current = current.link
   }
   if (current.getInfo() == target)  // current.info == target
      before.setLink(current.getLink()); // before.link = current.link
   
   else
      System.out.println("The target does not exist");

}
//.................................................................................
public void getTotalElement( )
{
	System.out.println ("Total Element is:");
	if (head ==null)
		System.out.println ("Zero");
	else
	{
		current = head;
		int count=0;
		while (current!=null)
		{
			current = current.getLink();
			count++;
}
System.out.println(count));
//.................................................................................
public void displayAllElement( )
{
	if (head ==null)
		System.out.println ("No Elements exist");
	else
	{
		System.out.println("All Elements Display");
		current = head;
		while (current!=null)
		{
			System.out.println(current.getInfo());
			current = current.getLink();
		}
	}
}
//.................................................................................
public void insertByTarget( )            
Node newNode = new Node(new Integer(5))
if (head == null)
  head = newNode;
else 
{
   if (head.getInfo()==target)
	head.setLink(newNode);
  else{
   Node current= head;
   while (current != null){
     if(current.getInfo()!= target)//current.info!=target
      current = current.getLink(); // current = current.link
     else if(current.getInfo() == target){ //current.info == target
	newNode.setLink(current.getLink()); //newNode.link=current.link
       current.setLink(newNode);  // current.link = newNode
       break; }
   if(current==null)
	System.out.println("The target does not exist");  }
  }
}         

//.................................................................................
public int deleteLast( )							//delete last link
{
		if (head == null)
		System.out.println("List is empty");
	else 
	{
		if (head.getLink ==null)
        head = null;
    else
    {
    	Node current = head;
    	
    while (current.getLink().getLink() !=null)
    	current = current.getLink();
    	current.setLink(null);
    }
    }

//.................................................................................
public void getFirstElement( ){
	if (head == null) 
	
		System.out.println ("First Element is Null");
	else
	{
		System.out.println("This is the First Element");
	
	
		System.out.println(head.getInfo());
	}
	}

public class List {

    public List() {
    }
    
 public static void main (String[] args)
{
LinkedList list = new LinkedList();
list.insertLast(new Integer(2));
list.deleteByTarget(new Integer(3), new Integer(3));
list. list.insertLast(new Integer(4));
list. list.insertLast(new Integer(5));
list.getTotalElement( );
list.displayAllElement( ); 
list.deleteLast( );
list. insertByTarget((new Integer(4), new Integer(5));
list. insertByTarget((new Integer(14), new Integer(4));
list. insertByTarget((new Integer(41), new Integer(14));
list.getLastElement( );
list.displayAllElement( );
      	
    }
//end main()
    
    
}
//end class ClassList

}
//////////////////////////////////////////////////////////////

/**The example of the output as shown below

--------------------Configuration: <Default>--------------------
AddFirst 3 successfull.
AddFirst 4 successfull.
AddLast 5 successfull.
AddLast 6 successfull.
Data : 4 3 5 6 
Remove By Target 6 successfull.
Data : 4 3 5 
AddFirst 7 successfull.
The target is not exists
Data : 7 4 3 5 
The first removed data is 7
The last removed data is 5
The last removed data is 3
Total element is 1
Data : 4 
First Element is 4
Last Element is 4

Process completed.
*/

[UnrealEd]

What seems to be the problem?