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
        if(head == null) return false;
        //先copy一个链表，再反转， 再比较
        ListNode reverseHead = new ListNode(head.val);
        ListNode tmp = head.next;
        ListNode newNodeNext = reverseHead;
        while(tmp != null){
            ListNode newNode = new ListNode(tmp.val);
            newNode.next = newNodeNext;
            newNodeNext = newNode;
            tmp = tmp.next;
            if(tmp == null) reverseHead = newNode;
        }
        while(reverseHead != null){
            if(reverseHead.val != head.val) return false;
            reverseHead = reverseHead.next;
            head = head.next;
        }
        return true;
    }
}

需要copy一个新的链表，然后反转该链表，再逐个比对