234. Palindrome Linked List [Easy] [Linked List | Two Pointers]
题意
Given a singly linked list, determine if it is a palindrome.
给定一个单链表，判断是否是“ 回文链表”。
Follow up:
Could you do it in O(n) time and O(1) space?
你能在时间复杂度 O(n) 和空间复杂度 O(1) 下完成该问题吗？
思路
提取链表中的 val, 加入到 list 中，然后进行判断。
# Definition for singly-linked list. # class ListNode(object): # def __init__(self, x): # self.val = x # self.next = None class Solution(object): def isPalindrome(self, head): """ :type head: ListNode :rtype: bool """ vals = [] while head: vals += head.val, head = head.next return vals == vals[::-1]