def removeDuplicates(head):
"""
:type head: ListNode
"""
flag = False
start = head
while start and start.next:
temp = start.next
if temp.val == start.val:
if not flag:
flag = True
start = start.next
else:
start.next = start.next.next
else:
flag = False
start = start.next
return head
第二题