剑指offer 15 链表中倒数第k个结点

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
def FindKthToTail(self, head, k):
# write code here
if head == None or k <= 0:
return None
res = head
count = 0
while head != None:
count += 1
if count > k:
res = res.next
head = head.next
if count < k:
return None
return res