删除链表中重复的结点

题目描述
在一个排序的链表中，存在重复的结点，请删除该链表中重复的结点，重复的结点不保留，返回链表头指针。 例如，链表1->2->3->3->4->4->5 处理后为 1->2->5

# -*- coding:utf-8 -*-
class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None
        
class Solution:
    def deleteDuplication(self, pHead):
        # write code here
        dummy = ListNode(-999999)
        p,q = dummy,pHead
        while q:
            if q.next and q.val==q.next.val:
                tv = q.val
                while q and q.val == tv: q=q.next
            else:
                p.next = q
                p = p.next
                q = q.next
        p.next=None
        return dummy.next