# Definition for singly-linked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class Solution:
def deleteDuplicates(self, head: ListNode) -> ListNode:
# 因为有序,不用缓冲区
if not head:
return None
pre = head
current = head.next
while current:
if pre.val == current.val:
pre.next = current.next
else:
pre = current
current = current.next
return head