题解 | #快慢指针# #链表中倒数最后k个结点#

#coding:utf-8
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param pHead ListNode类 
# @param k int整型 
# @return ListNode类
#
class Solution:
    def FindKthToTail(self , pHead , k ):
        # write code here

        #init
        fast = pHead
        slow = pHead

        #process
        ##corner case
        if pHead == None:
            return None
        size = 0
        dummy = pHead
        while dummy != None:
            size += 1
            dummy = dummy.next
        #print ("Size is: ", size)
        if size < k:
            return None

        ##common case
        for i in range(0, k):
            fast = fast.next
        while fast != None:
            fast = fast.next 
            slow = slow.next 
            #print ("Slow val: ")

        return slow