题解 | #牛群编号的回文顺序II#

链表遍历操作的考察

对于链表遍历后得到字符串表示，然后对于字符串找到最大回文串，再根据最大回文串的结果重新构建链表返回

完整Java代码如下

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
     * @return ListNode类
     */
    public ListNode maxPalindrome (ListNode head) {
        // write code here
        StringBuffer stringBuffer = new StringBuffer();
        while (head != null) {
            stringBuffer.append(head.val);
            head = head.next;
        }
        if (isParame(stringBuffer.toString())) {
            return null;
        }
        ListNode result = null;
        int length = 0;
        for (int i = 0; i < stringBuffer.length(); i++) {
            for (int j = i + 1; j <= stringBuffer.length(); j++) {
                String string = stringBuffer.substring(i, j);
                if (string.length() > length && isParame(string)) {
                    length = string.length();
                    ListNode node = new ListNode(0);
                    result = node;
                    for (int k = 0; k < string.length(); k++) {
                        node.next = new ListNode(string.charAt(k) - '0');
                        node = node.next;
                    }
                }
            }
        }
        return result.next;
    }

    public static boolean isParame(String s) {
        StringBuilder stringBuffer = new StringBuilder();
        stringBuffer.append(s);
        return stringBuffer.reverse().toString().equals(s);
    }

}