Question

I want to remove duplicates from sorted linked list {0 1 2 2 3 3 4 5}.

`

public Node removeDuplicates(Node header)
{
    Node tempHeader = null;
    if(header != null) 
        tempHeader = header.next;
    else return header;
    Node prev = header;
    if((tempHeader == null)) return header ;

    while(tempHeader != null)
    {
        if(tempHeader.data != prev.data)
        {
            prev.setNext(tempHeader);
        }
    tempHeader = tempHeader.next;
    }
    prev = header;
    printList(prev);
    return tempHeader;
}

`

prev.setNext(tempHeader) is not working correctly inside the while loop. Ideally when prev = 2 and tempHeader = 3, prev.next should be node with data = 3.

Printlist function just takes header pointer and prints the list.

Node definition is given below.

public class Node
{
    int data;
    Node next;

    public Node getNext() {
        return next;
    }
    public void setNext(Node next) {
        this.next = next;
    }
}

Answer 1

The loop is sorted, so you know that duplicates are going to sit next to each other. If you want to edit the list in place then, you’ve got to have two list pointers (which you do). The one you call tempHeader and prev, and you’ve got to advance them both in the the list as you go (which I don’t see in the code). Otherwise, if you don’t advance the prev pointer as you go, then you’re always comparing the element under tempHeader to the first item in the list, which is not correct.

An easier way to do this, however, is to build a new list as you go. Simply remember the value of the last item that you appended to the list. Then if the one that you’re about to insert is the same then simply don’t insert it, and when you’re done, just return your new list.