删除有序链表中重复的元素-1

# 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 
               
        cur = head
        
        while cur and cur.next:
            if cur.val == cur.next.val:
                cur.next = cur.next.next
            else:
                cur = cur.next
        
        return head
        
        
#         while cur:
#             if cur not in visited:
#                 visited[cur] = head
#             else:
#                 pre.next = cur.next
#                 cur = cur.next