剑指Offer 22 链表中倒数第k个节点

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 None
13         safehead = ListNode(head.val)
14         safehead.next = head.next
15         fast = head
16         count = 0
17         while count != k:
18             if fast == None:
19                 return None
20             fast = fast.next
21             count += 1
22         slow = safehead
23         while fast != None:
24             fast = fast.next
25             slow = slow.next
26         return slow