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 {
    /**
     * 1 2 2 1 --> 1 2 2 1
     * 
     *
     * @param head ListNode类 the head
     * @return bool布尔型
     */
    public boolean isPail (ListNode head) {
        if (head == null || head.next == null) {
            return true;
        }

        // 先把所有的节点放入到Stack中
        Stack<ListNode> stack = new Stack<>();
        ListNode tempNode = head;
        stack.push(tempNode);
        while (tempNode.next != null) {
            tempNode = tempNode.next;
            stack.push(tempNode);
        }

        tempNode = head;
        while(!stack.isEmpty()) {
            if(stack.pop().val != tempNode.val) {
                return false;
            }
            tempNode = tempNode.next;
        }
        return true;
    }
}