删除有序链表中重复的元素-II

用递归对其进行判断即可

public ListNode deleteDuplicates (ListNode head) {
        // write code here

        if(head==null) return null;

        if (head.next!=null&&head.val==head.next.val){
            while (head.next!=null&&head.val==head.next.val){
                head.next=head.next.next;
            }
            return deleteDuplicates(head.next);
        }

        head.next=deleteDuplicates(head.next);
        return head;

    }