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) {
        Integer[] arr = new Integer[ListNodeLenth(head)];
        ListNode temp = head;
        int i = 0;
        while (temp != null) {
            arr[i] = temp.val;
            i++;
            temp = temp.next;
        }

        int left = 0;
        int right = arr.length - 1;
        int mid = arr.length / 2;


        while (left < right) {
            if (!arr[left].equals(arr[right])) {
                return false;
            }
            left++;
            right--;
        }
        return true;
    }


     public int ListNodeLenth(ListNode pHead) {
        if (pHead == null) {
            return 0;
        }
        ListNode temp = pHead;
        int len = 1;
        while (temp.next != null) {
            temp = temp.next;
            len++;
        }
        return len;
    }
}

回文有left<right和while(count<mid) 都是一样操作一样的次数.

先是把链表的数值放到数组中,之后使用left和right进行操作.