LeetCode 234: Palindrome Linked List Solution

class Solution {
    public boolean isPalindrome(ListNode head) {
        ListNode slow = head;
        ListNode fast = head;
        
        // Find the middle of the linked list
        while (fast != null && fast.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        
        // Reverse the second half of the linked list
        ListNode prev = null;
        ListNode curr = slow;
        while (curr != null) {
            ListNode nextTemp = curr.next;
            curr.next = prev;
            prev = curr;
            curr = nextTemp;
        }
        
        // Compare the first half with the reversed second half
        ListNode firstHalf = head;
        ListNode secondHalf = prev;
        while (secondHalf != null) {
            if (firstHalf.val != secondHalf.val) {
                return false;
            }
            firstHalf = firstHalf.next;
            secondHalf = secondHalf.next;
        }
        
        return true;
    }
}