链表的倒数第k个结点

public class Solution {
    public ListNode FindKthToTail(ListNode head,int k) {
        if(k<=0){
            return null;
        }
        if(head==null){
            return null;
        }
            ListNode fast=head;
            ListNode slow=head;
            while(k-1!=0){
                fast=fast.next;
                if(fast==null){
                    return null;
                }
                k--;
            }
            while(fast.next!=null){
                    fast=fast.next;
                    slow=slow.next;
            }
            return slow;
    }
}