CareerCup 2.1 Write code to remove duplicates from an unsorted linked list. FOLLOW UP How would you solve this problem if a temporary buffer is not allowed?

Solution.java

import java.util.HashSet;

public class Solution {
	
	
	public static void deleteDuplicates_HashSet(Node head){
		HashSet<Integer> nodeSet = new HashSet<Integer>();
		
		Node prev = null;
		while(head != null){
			if(nodeSet.contains(head.data)){
				prev.next = head.next;
			}
			else{
				nodeSet.add(head.data);
				prev = head;
			}
			head = head.next;
		}//end of while
		
	}//end of deleteDuplicates_HashSet
	
	//iterate with two pointers:
	//1.current which iterate through the linked list
	//2. runner which checks all subsequent node for duplicates
	public static void deleteDuplicates_runner(Node head){
		
		Node cur = head;
		
		while(cur != null){
			Node runner = cur;
			while(runner.next != null){
				if(cur.data == runner.next.data){
					runner.next = runner.next.next;
				}
				else{
					runner = runner.next;
				}				
			}//end of while runner
			cur = cur.next;
		}//end of while cur
		
	}
}