83. Remove Duplicates from Sorted List（python）__python

Given a sorted linked list, delete all duplicates such that each element appear only once.
For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.
題意：排序的鏈表重複資料刪除的元素，保證每個元素出現一次
runtime:68ms
總結：val不同的，移動指標p，val相同的,指標p不變，移動p.next;
每一次比較p.next.val和p.val之前，都要先判斷p.next存在與否，否則p.next=None時，p.next.val會報錯

# Definition for singly-linked list.# class ListNode(object):#     def __init__(self, x):#         self.val = x#         self.next = Noneclass Solution(object):    def deleteDuplicates(self, head):        if not head or not head.next:            return head        dummy=ListNode(0)        dummy.next=head        p=head        while p.next:            if p.next.val==p.val:                p.next=p.next.next            else:                p=p.next        return dummy.next