lintcode 173 单链表插入排序 python

"""Definition of ListNodeclass ListNode(object):    def __init__(self, val, next=None):        self.val = val        self.next = next"""class Solution:    """    @param head: The first node of linked list.    @return: The head of linked list.    """     def insertionSortList(self, head):        # write your code here        if head.next is None:return head        prehead = head  #定义temp为拟排序节点        temp = head.next        if temp is not None:prenext = temp.next        else:prenext = None        flag = 0  #标记是否对temp做了排序        while temp:            nowhead = head #定义nownode 为对比节点            nownode = head.next            if temp.val < head.val:   #首先对比head的值进行判断                temp.next = head                head = temp                temp = prenext                prehead.next = prenext                if temp is not None:prenext = temp.next                else:prenext = None                continue            while nownode != temp:  #然后循环对比temp前的所有节点                if temp.val < nownode.val:                    flag = 1                    nowhead.next = temp                    temp.next = nownode                    prehead.next = prenext                    temp = prenext                    if temp is not None:prenext = temp.next                    else:prenext = None                    break                else:                    nowhead = nownode                    nownode = nownode.next            if flag == 0:                prehead = temp                temp = prenext                if temp is not None:prenext = temp.next                else:prenext = None            flag = 0        return head