CODEWITHSUNDEEP
javasingly-linked-listis-empty
mario vergo
mario vergo

Reputation: 49

Singly linked list empty check

I have created this Node class for a singly linked list:

 class Node{
   int item; 
   Node next;
   Node(int v){
     item = v;
     next = null; 
   }
 }



I want to make a search for the node with the highest key in a method called findmax.But i want to check if the list is empty, and if so , to return null, otherwise return the node with the highest key. This is what i have done:

Node findmax(Node h){
  if(h==null)
    return null;
  else{
  //search 
  }

All i want to know is if the check i make to see if the list is Empty is correct.

Upvotes: 2

Views: 10045

Answers (1)

Giulio Biagini
Giulio Biagini

Reputation: 920

Yes, the check you've done is correct if:

Node n = null;// init empty list

and:

n = new Node(3);// first item

However, I suggest you to create a list struct which is independent from the item it concatenates. That's what I mean:

The Node class:

public class Node
{
    int value;

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

    public int getValue() {
        return value;
    }
}

The list struct:

public interface IList
{
    public int getNodeNumbers();
}

public class EmptyList implements IList
{
    @Override public int getNodeNumbers() {
        return 0;
    }
}

public class ConsList implements IList
{
    private Node node;

    private IList next;

    public ConsList(Node node, IList next) {
        this.node = node;
        this.next = next;
    }

    @Override public int getNodeNumbers() {
        return 1 + next.getNodeNumbers();
    }
}

How to use it:

public class Main
{
    public static void main(String[] args) {
        IList list1 = new ConsList(new Node(1),
            new ConsList(new Node(2),
            new ConsList(new Node(3),
            new ConsList(new Node(4),
            new EmptyList()))));

        IList list2 = new EmptyList();

        System.out.println(list1.getNodeNumbers() + " - " + list2.getNodeNumbers());
    }
}

And now, a list is empty (you can create your own method isEmpty() into the IList interface) when getNodeNumbers() returns 0.

Upvotes: 0

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