题解 | #删除链表的倒数第n个节点#

public static ListNode removeNthFromEnd (ListNode head, int n) {

        if (getLength(head) == n){
            head = head.next;
            return head;
        }

        ListNode p = head, q = head;
        int i = 0;

        // 找出前后两个游标之间的距离 == n,然后连个游标不断往后移动，直到后面的游标的next为null停止
        while (i < n){
            q = q.next;
            i++;
        }

        while (q.next != null){
            q = q.next;
            p = p.next;
        }
        p.next = p.next.next;
        return head;

    }

    public static int getLength(ListNode head){
        int i = 0;
        ListNode p = head;
        while (p != null){
            i++;
            p = p.next;
        }
        return i;
    }