# 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:
        if head == None:
            return None
        # 遍历指针
        cur = head
        # 指针当前和下一位不为空
        while cur and cur.next:
            # 如果当前与下一位相等则忽略下一位
            if cur.val == cur.next.val:
                cur.next = cur.next.next
            # 否则指针正常遍历
            else:
                cur = cur.next
        return head