83. 删除排序链表中的重复元素

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def deleteDuplicates(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if head == None or head.next == None:
            return head
        i = head
        while i:
            while i.next and i.val == i.next.val:
                i.next = i.next.next
            i = i.next
        return head