快慢指针判断是不是回文链表

import java.util.*;

/*

* public class ListNode {

* int val;

* ListNode next = null;

* }

*/

public class Solution {

public boolean isPail(ListNode head) {

ListNode slow = head;

ListNode fast = head;

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

fast = fast.next.next;

slow = slow.next;

}

ListNode curr1 = reverse(slow);

ListNode curr2 = head;

while (curr1 != null) {

if (curr1.val != curr2.val) {

return false;

}

curr1 = curr1.next;

curr2 = curr2.next;

}

return true;

}

private ListNode reverse(ListNode node) {

ListNode prev = null;

ListNode curr = node;

while (curr != null) {

ListNode temp = curr.next;

curr.next = prev;

prev = curr;

curr = temp;

}

return prev;

}

 

}