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
        pre = post = head
        for i in range(k):
            if pre == None:
                return None
            pre = pre.next
        while pre != None:
            pre = pre.next
            post = post.next
        return post