算法:链表中倒数第k个结点

while (fast != null && --k >= 0) {
    fast = fast.next;
}
if (fast == null) return k == 0 ? slow : null;

public class Solution {
    public ListNode FindKthToTail(ListNode head,int k) {
        if (head == null || k <= 0) return null;

        ListNode fast = head, slow = head;
        while (fast != null && --k >= 0) {
            fast = fast.next;
        }
        if (fast == null) return k == 0 ? slow : null;

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