Swap Kth nodes from ends

class Node {
    int data;
    Node next;

    Node(int x) {
        data = x;
        next = null;
    }
}

class Solution {
    public Node swapKth(Node head, int k) {
        Node f_num = head;
        Node l_num = head;

        int c = countNode(head);
        int x = c - k + 1;

        if (k > c)
            return head;

        while (k > 0) {
            k--;
            if (k > 0)
                f_num = f_num.next;
        }

        while (x > 0) {
            x--;
            if (x > 0)
                l_num = l_num.next;
        }

        int temp = f_num.data;
        f_num.data = l_num.data;
        l_num.data = temp;

        return head;
    }

    private int countNode(Node head) {
        int c = 0;
        while (head != null) {
            c++;
            head = head.next;
        }

        return c;
    }
}