leetcode之Palindrome Linked List

这道题一开始想到的比较简单。但是follow up的比较难，暂时没有想出来如何出现O(1)的space。代码如下：

# Definition for singly-linked list.# class ListNode(object):#     def __init__(self, x):#         self.val = x#         self.next = Noneclass Solution(object):    def isPalindrome(self, head):        """        :type head: ListNode        :rtype: bool        """        if head == None:            return True        b = []        while head.next != None:            b.append(head.val)            head = head.next        b.append(head.val)        if b == b[::-1]:            return True        else:            return False