LeetCode -- Palindrome Linked List

题目描述：


Given a singly linked list, determine if it is a palindrome.


Follow up:
Could you do it in O(n) time and O(1) space?




即判断链表是否为回文。


思路：只能想到借助队列，没能达到空间复杂度O(1)，空间复杂度O(N)


实现代码：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public bool IsPalindrome(ListNode head) {
        if(head == null || head.next == null){
            return true;
        }
        
        var list = new List<int>();
        while(head != null){
            list.Add(head.val);
            head = head.next;
        }
        
        for(var i =0 ;i < list.Count/2; i++){
            if(list[i] != list[list.Count-i-1]){
                return false;
            }
        }
        
        return true;
    }
}