题解 | #链表中倒数最后k个结点# 快慢指针法

    public ListNode FindKthToTail (ListNode head, int k) {
        if(head==null) return head;
        // 先定义一个prev前缀节点
        ListNode prev = new ListNode(0);
        prev.next = head;
        ListNode slow = prev, fast = head;
        // 先让fast走k步
        while(k-->0&&fast!=null){
            fast = fast.next;
        }
        if(fast==null&&k>=0) return null;
        while(fast!=null){
            fast = fast.next;
            slow = slow.next;
        }
        return slow.next;
    }