Linked List Problems

public boolean isPalindrome() {
    // Find middle
    Node slow = head, fast = head;
    while (fast != null && fast.next != null) {
        slow = slow.next;
        fast = fast.next.next;
    }
    // Reverse second half
    Node prev = null;
    Node curr = slow;
    while (curr != null) {
        Node next = curr.next;
        curr.next = prev;
        prev = curr;
        curr = next;
    }
    // Compare first half and reversed second half
    Node first = head;
    Node second = prev;
    while (second != null) {
        if (first.data != second.data) return false;
        first = first.next;
        second = second.next;
    }
    return true;
}

public static Node mergeSorted(Node l1, Node l2) {
    Node dummy = new Node(0);
    Node tail = dummy;
    while (l1 != null && l2 != null) {
        if (l1.data < l2.data) {
            tail.next = l1;
            l1 = l1.next;
        } else {
            tail.next = l2;
            l2 = l2.next;
        }
        tail = tail.next;
    }
    tail.next = (l1 != null) ? l1 : l2;
    return dummy.next;
}