/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isPalindrome(ListNode head) {
ListNode fast = head;
ListNode slow = head;
while (fast != null && fast.next != null) {
fast = fast.next.next;
slow = slow.next;
}
if (fast != null) slow = slow.next;
slow = reverse(slow);
ListNode tHead = head;
while (slow != null) {
if (slow.val != tHead.val) return false;
slow = slow.next;
tHead = tHead.next;
}
return true;
}
public ListNode reverse(ListNode head) {
ListNode newHead = null;
while (head != null) {
ListNode next = head.next;
head.next = newHead;
newHead = head;
head = next;
}
return newHead;
}
}
