Remove duplicates from an unsorted linked list

Question

import java.util.*;
/*
 *  Remove duplicates from an unsorted linked list
 */
public class LinkedListNode {  
    public int data;  
    public LinkedListNode next;          


        

Answer 1

1. The solution you have provided does not modify the original list.
2. To modify the original list and remove duplicates, we can iterate with two pointers. Current: which iterates through LinkedList, and runner which checks all subsequent nodes for duplicates.

3. The code below runs in O(1) space but O(N square) time.

   public void deleteDups(LinkedListNode head){

   if(head == null)
       return;
   
   LinkedListNode currentNode = head;       
   while(currentNode!=null){
       LinkedListNode runner = currentNode;
       while(runner.next!=null){
           if(runner.next.data == currentNode.data)
               runner.next = runner.next.next;
           else
               runner = runner.next;
       }
       currentNode = currentNode.next;
   }
   

   }

Reference : Gayle laakmann mcdowell