输入一个链表，输出该链表中倒数第k个结点。

1 # -*- coding:utf-8 -*- 2 # class ListNode: 3 #     def __init__(self, x): 4 #         self.val = x 5 #         self.next = None 6  7 class Solution: 8     def FindKthToTail(self, head, k): 9         fast = ListNode(0)10         slow = ListNode(0)11         if head == None:12             return None13         safehead = ListNode(head.val)14         safehead.next = head.next15         fast = head16         count = 017         while count != k:18             if fast == None:19                 return None20             fast = fast.next21             count += 122         slow = safehead23         while fast != None:24             fast = fast.next25             slow = slow.next26         return slow