DeleteDuplicates.java

public ListNode deleteDuplicates(ListNode head) {
        
  if(head == null || head.next == null) 
    return head;
        
  ListNode current = head;
  while(current != null && current.next != null){
    if(current.val == current.next.val){
      current.next = current.next.next;
    }else{
      current = current.next;
    }
   }
   return head;
}