题解 | #判断一个链表是否为回文结构#

快慢指正

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) {
        if (head == null || head.next == null) {
            return true;
        }
        ListNode slow = head;
        ListNode fast = head.next;
        ListNode p = null;

        while(fast != null && fast.next != null) {
            ListNode t = slow.next;
            slow.next = p;
            p = slow;
            slow = t;
            fast = fast.next.next;
        }
        ListNode right = slow.next;
        slow.next = p;
        if (fast == null) {
            slow = slow.next;
        }
        while(right != null) {
            if (right.val != slow.val) {
                return false;
            }
            right = right.next;
            slow = slow.next;
        }

        return true;
    }
}