19. Remove Nth Node From End of List

class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode fast = head , slow = head;
        for (int i=0 ; i<n ; i++){ fast = fast.next; }
        if (fast == null) return head.next;
        while (fast.next!=null){
                fast = fast.next ;
                slow = slow.next;
        }
        slow.next = slow.next.next;
        return head;
    }
}