[LeetCode]题解（python）：061-Rotate list

Given a list, rotate the list to the right by k places, where k is non-negative.

For example:
Given 1->2->3->4->5->NULL and k = 2,
return 4->5->1->2->3->NULL.

Output:a list of node shift to right

Conditions:链表右移

PS：对于链表操作，每次在前面添加一个节点这个方法很好用，特别注重边界条件

PS2：尽量用xrange代替range

 1 __author__ = ‘YE‘
 2
 3 # Definition for singly-linked list.
 4 class ListNode(object):
 5     def __init__(self, x):
 6         self.val = x
 7         self.next = None
 8
 9 class Solution(object):
10     def rotateRight(self, head, k):
11         """
12         :type head: ListNode
13         :type k: int
14         :rtype: ListNode
15         """
16         if k == 0 or head == None:
17             return head
18
19         addFirst = ListNode(0)
20         addFirst.next = head
21         # move variable
22         p = addFirst
23         #the length of list
24         count = 0
25         while p.next != None:
26             p = p.next
27             count += 1
28         p.next = addFirst.next
29         #the real step to shift right
30         step = count - (k % count)
31         p = addFirst.next
32         for i in xrange(1, step):
33             p = p.next
34         head = p.next
35         p.next = None
36
37         return head