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 ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param head ListNode类 the head
     * @return bool布尔型
     */
    public boolean isPail (ListNode head) {
        // write code here

        ListNode dummy = new ListNode(-1);
        ListNode result = dummy;

        ListNode cur = head;
        ListNode pre = null;

        while (cur != null) {
            dummy.next = new ListNode(cur.val);
            dummy = dummy.next;
            ListNode next = cur.next;
            cur.next = pre;
            pre = cur;
            cur = next;
        }

        head = result.next;
        boolean flag = true;
        while (head != null && pre != null) {
            int val1 = head.val;
            int val2 = pre.val;

            if (val1 != val2) {
                flag = false;
                break;
            }
            head = head.next;
            pre = pre.next;
        }
        return flag;
    }
}