题解 | #判断一个链表是否为回文结构#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     *
     * @param head ListNode类 the head
     * @return bool布尔型
     */
    public boolean isPail (ListNode head) {
        ArrayList<ListNode> list = new ArrayList<>();
        while (head != null) {
            list.add(head);
            head = head.next;
        }
        int size = list.size();
        if (size % 2 == 0) {
            int r = size / 2;
            int l = r - 1;
            while (l >= 0) {
                if (list.get(l).val != list.get(r).val) return false;
                l--;
                r++;
            }
            return true;
        } else {
            int r = size / 2 + 1;
            int l = size / 2 - 1;
            while (l >= 0) {
                if (list.get(l).val != list.get(r).val) return false;
                l--;
                r++;
            }
            return true;
        }
    }
}