给定一个排序链表，删除所有重复的元素，使得每个元素只出现一次。
示例 1:
输入: 1->1->2 输出: 1->2
示例 2:
输入: 1->1->2->3->3 输出: 1->2->3
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, x):
# self.val = x
# self.next = Noneclass Solution:def deleteDuplicates(self, head):""":type head: ListNode:rtype: ListNode"""#第一种
# while head is None:
# return head# p = head
# current_node = head.next# while current_node:
# if p.val < current_node.val:
# p = current_node
# current_node = current_node.next
# else:
# p.next = current_node.next #插入
# current_node = current_node.next
# return head#第二种 while head is None:return headp = headwhile p and p.next:if p.val == p.next.val:p.next = p.next.nextelse:p = p.nextreturn head