题解 | #删除有序链表中重复的元素-I#

# 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
#
# 用 ans 节点建立一个新链表，其中仅保存第一次出现的值的节点
class Solution:
    def deleteDuplicates(self , head: ListNode) -> ListNode:
        if head == None or head.next == None:
            return head

        preValue = head.val
        ans = head
        ansNode = ans
        head = head.next
        while head != None:
            if head.val == preValue:
                head = head.next
            else:
                preValue = head.val
                ans.next = head
                ans = ans.next
        ans.next = None
        return ansNode