题解 | #链表中倒数最后k个结点#

# 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 ):
        fast = pHead
        slow = pHead
        #快指针先行k步
        for i in range(0,k): 
            if fast != None:
                fast = fast.next
            #达不到k步说明链表过短，没有倒数k
            else: 
                return None
        #快慢指针同步，快指针先到底，慢指针指向倒数第k个
        while fast:
            fast = fast.next
            slow = slow.next
        return slow