题解 | #删除有序链表中重复的元素-II#

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param head ListNode类 
# @return ListNode类

class Solution:
    def deleteDuplicates(self , head: ListNode) -> ListNode:
        # write code here
        if not head:
            return head
        list1=[]
        s=set()
        while head:
            list1.append(head.val)                                                       
            s.add(head.val)
            head=head.next
        for i in range(len(list1)-1):
            if list1[i]==list1[i+1]:
                if list1[i] in s:
                    s.remove(list1[i])
        s=list(s)
        s.sort()
        if not s:
            return None
        lend=cur=ListNode(s[0])
        for i in range(1,len(s)):
            cur.next=ListNode(s[i])
            cur=cur.next
        return lend