def deleteDuplicates(head: ListNode) -> ListNode:if not head:return headdummy = ListNode(0)dummy.next = headcur = head.nextwhile cur:if cur.val != head.val:head.next = curhead = curelse:head.next = None # 如果当前值与head的值相等，需要断开cur = cur.nextreturn dummy.nextdef deleteDuplicates2(head: ListNode) -> ListNode:cur = headwhile cur and cur.next: # 如果不是最后一个，cur为None是排除[]的情况if cur.val == cur.next.val:cur.next = cur.next.next # delete duplicate elementelse:cur = cur.nextreturn head