234. 回文链表

刺骨的言语ヽ痛彻心扉 2022-09-08 00:21 118阅读 0赞

[https://leetcode-cn.com/problems/palindrome-linked-list/][https_leetcode-cn.com_problems_palindrome-linked-list]

难度简单1087

给你一个单链表的头节点 `head` ，请你判断该链表是否为回文链表。如果是，返回 `true` ；否则，返回 `false` 。

**示例 1：**

![70b052810fbc7389fc6c77e5f8a7f388.png][]

输入：head = [1,2,2,1]
    输出：true

**示例 2：**

![2ecd174396cb07fbc62c7c4f0a851623.png][]

输入：head = [1,2]
    输出：false

**提示：**

*  链表中节点数目在范围`[1, 105]` 内
 *  `0 <= Node.val <= 9`

**进阶：**你能否用 `O(n)` 时间复杂度和 `O(1)` 空间复杂度解决此题？

通过次数293,160提交次数595,792

/**
     * Definition for singly-linked list.
     * public class ListNode {
     *     int val;
     *     ListNode next;
     *     ListNode() {}
     *     ListNode(int val) { this.val = val; }
     *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
     * }
     */
    class Solution {
        public boolean isPalindrome(ListNode head) {
            List<Integer> num = new ArrayList<Integer>();
            while(head!=null)
            {
                num.add(head.val);
                head = head.next;
            }
            for(int i=0,j=num.size()-1;i<j;i++,j--)
            {
                if(num.get(i)!=num.get(j)) return false;
            }
            return true;
        }
    }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_Q1NETiBA5Yqq5Yqb5a2m5Lmg55qE5qKF5a2Q_size_18_color_FFFFFF_t_70_g_se_x_16][]

[https_leetcode-cn.com_problems_palindrome-linked-list]: https://leetcode-cn.com/problems/palindrome-linked-list/
[70b052810fbc7389fc6c77e5f8a7f388.png]: /images/20220829/95341cafc0d44150b1957ffc324f8bac.png
[2ecd174396cb07fbc62c7c4f0a851623.png]: /images/20220829/48320bd8e50e44608e0aa359b71472cf.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_Q1NETiBA5Yqq5Yqb5a2m5Lmg55qE5qKF5a2Q_size_18_color_FFFFFF_t_70_g_se_x_16]: /images/20220829/4960916eac3143729ac53fb99be33715.png