算法--链表的回文结构

import java.util.*;

/*

public class ListNode {

    int val;

    ListNode next = null;

    ListNode(int val) {

        this.val = val;

    }

}*/

public class Palindrome {

    public boolean isPalindrome(ListNode pHead) {

        if (pHead == null || pHead.next == null)

            return false;

        ListNode slow = pHead;

        ListNode quick = pHead;

        Stack<Integer> stack = new Stack<>();

        while (quick != null && quick.next != null) {

            stack.push(slow.val);

            slow = slow.next;

            quick = quick.next.next;

        }

        /**

         * 5 7 3 2 3 7 5

         * 4 3 2 1 1 2 3 4

         */

        if (quick != null && quick.next == null) {

            slow = slow.next;

            // stack.pop();

        }

        while (!stack.isEmpty() && slow != null) {

            int val = stack.pop();

            // System.out.print(val + " ");

            if (val != slow.val)

                return false;

            slow = slow.next;

        }

        return true;

    }

}