Java

   public static Node removeDuplicates(Node head) {
         if(head==null||head.next==null){
    return head;
  }

  List<Integer> list = new ArrayList<>();
  Node current = head;
  while(current.next!=null){
    list.add(current.data); 
     if(list.contains(current.next.data)){
        // skip the next node
        current.next = current.next.next;                  
        }else {
            current = current.next;
        }         
  }
  return head;
}