删除链表的倒数第n个节点

依旧是双指针; 移动指针后针对具体条件进行判断即可

 public ListNode removeNthFromEnd (ListNode head, int n) {
        // write code here
         ListNode fast=head;
        ListNode slow=head;
        for (int i=0;i<n;i++){
            if(fast==null) return null;
            fast=fast.next;
        }


       if(fast==null) return head.next;
       else {
           while (fast.next!=null){
               fast=fast.next;
               slow=slow.next;
           }
       }

       slow.next=slow.next.next;
       return head;
    }