1 # -*- coding:utf-8 -*-
2 # class ListNode:
3 # def __init__(self, x):
4 # self.val = x
5 # self.next = None
6
7 """双指针的关键是如何保持指针的距离为k-1"""
8 class Solution:
9 def FindKthToTail(self, head, k):
10 # write code here
11 if head == None or k==0:
12 return None
13 phead = head
14 pbehind = head
15 for i in range(k-1): #range的数字之差代表元素个数
16 if phead.next == None:
17 return None
18 else:
19 phead = phead.next
20 while phead.next != None: #倒数第二个节点依然满足，因此最终的phead是最后一个，最终的pbehind就是倒数第k个
21 phead = phead.next
22 pbehind = pbehind.next
23 return pbehind
24
25
26 """直接用列表实现"""
27 # -*- coding:utf-8 -*-
28 # class ListNode:
29 # def __init__(self, x):
30 # self.val = x
31 # self.next = None
32
33 class Solution:
34 def FindKthToTail(self, head, k):
35 # write code here
36 l = []
37 while head:
38 l.append(head)
39 head = head.next
40 if len(l) < k or k < 1:
41 return None
42 return l[-k]
