83. Remove Duplicates from Sorted List

 public ListNode DeleteDuplicates(ListNode head) {
        if(head == null) return head;
        
        ListNode dn= head; 
        
        while((head != null)&&(head.next!= null))
        {
            if(head.next.val == head.val)
            {
                head.next = head.next.next;
            }
            else
            {
                head = head.next;
            }
        }
        
        return dn;
    }

Given a sorted linked list, delete all duplicates such that each element appear only once.

For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.