19. Remove Nth Node From End of List (Medium)-

删除链表的倒数第 n 个节点

Given linked list: 1->2->3->4->5, and n = 2.
After removing the second node from the end, the linked list becomes 1->2->3->5.

public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode l1 = dummy;
        ListNode l2 = dummy;
        
        while(l2 != null){
            if(n < 0){
               l1 = l1.next;
            }
            l2 = l2.next;
            n--;
        }
        l1.next = l1.next.next;
        return dummy.next;
    }