# # 【LeetCode】61. Rotate List 解题报告（Python）

## # 题目描述：

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

Example 1:

``````Input: 1->2->3->4->5->NULL, k = 2
Output: 4->5->1->2->3->NULL
Explanation:
rotate 1 steps to the right: 5->1->2->3->4->NULL
rotate 2 steps to the right: 4->5->1->2->3->NULL
``````

Example 2:

``````Input: 0->1->2->NULL, k = 4
Output: 2->0->1->NULL
Explanation:
rotate 1 steps to the right: 2->0->1->NULL
rotate 2 steps to the right: 1->2->0->NULL
rotate 3 steps to the right: 0->1->2->NULL
rotate 4 steps to the right: 2->0->1->NULL
``````

## # 解题方法

``````# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
"""
:type k: int
:rtype: ListNode
"""
_len = 0
_len += 1
k %= _len
if k == 0: return root
fast, slow = root, root
while k - 1:
fast = fast.next
k -= 1
pre = slow
while fast.next:
fast = fast.next
pre = slow
slow = slow.next
pre.next = None
fast.next = root
return slow
``````

## # 日期

2018 年 6 月 23 日 ———— 美好的周末要从刷题开始