[LeetCode] 19. 删除链表的倒数第N个节点 ☆☆☆

public static ListNode removeNthFromEnd(ListNode head, int n) {
        if (null == head || n <= 0) {
            return head;
        }
        ListNode slowPre = head;//比slow节点慢1个位置
        ListNode slow = head;//比fast节点慢n个位置
        ListNode fast = head;
        int slowCount = 0;
        while (null != fast) {
            if (n > 0) {
                fast = fast.next;
                n--;
                if (n == 0 && null == fast) {//当倒数第n个节点,刚好是首节点,直接返回head.next
                    return head.next;
                }
            } else {
                fast = fast.next;
                slow = slow.next;
                if (slowCount == 1) {
                    slowPre = slowPre.next;
                } else {
                    slowCount++;
                }
            }
        }
        slowPre.next = slow.next;
        return head;
    }