gistfile1.java

import java.util.HashSet;
import java.util.Set;

public class FindDuplicateLL {

	public static void main( String[] args ) {
		LinkNode head = new LinkNode( 1 );
		head.append( new LinkNode( 2 ) );
		head.append( new LinkNode( 3 ) );
		head.append( new LinkNode( 1 ) );
		head.append( new LinkNode( 5 ) );

		printLinkedList( head );
		removeDuplicateNodeNoBuffer( head );
		System.out.println( head.getValue() );
		printLinkedList( head );

	}

	public static void printLinkedList( LinkNode head ) {
		while ( head != null ) {
			System.out.print( head.getValue() );
			System.out.print( "->" );
			head = head.getNext();
		}

		System.out.println( "null" );

	}

	public static void removeDuplicateNode( LinkNode head ) {
		HashSet<Integer> set = new HashSet<>();
		LinkNode p = null;

		while ( head != null ) {
			if ( set.contains( head.getValue() ) )
				p.setNext( head.getNext() );
			else {
				p = head;
				set.add( head.getValue() );
			}
			head = head.getNext();
		}
	}

	public static void removeDuplicateNodeNoBuffer( LinkNode head ) {
		if ( head == null )
			return;

		LinkNode p1 = head;
		while ( p1!= null ) {
			LinkNode p2 = p1;
			while ( p2.getNext() !=  null ) {
				if ( p2.getNext().getValue() != p1.getValue() )
					p2 = p2.getNext();
				else p2.setNext( p2.getNext().getNext() );
			}
			p1 = p1.getNext();
		}
	}
}

gistfile2.java

public class LinkNode {

    private int value;
	private LinkNode next;

	public LinkNode( int val ) {
		this.value = val;
		this.next = null;
	}

	public int getValue() {
		return value;
	}

	public void setValue( int value ) {
		this.value = value;
	}

	public LinkNode getNext() {
		return next;
	}

	public void setNext( LinkNode n ) {
		this.next = n;
	}

	public void append( LinkNode n ) {
		LinkNode currNode = this;
		while ( currNode.next != null ) {
			currNode = currNode.next;
		}
		currNode.next = n;
	}

}