LeetCode189. Rotate Array

Given an array, rotate the array to the right by k steps, where k is non-negative.

Example 1:

Input: 
[1,2,3,4,5,6,7]
 and k = 3
Output: 
[5,6,7,1,2,3,4]

Explanation:
rotate 1 steps to the right: 
[7,1,2,3,4,5,6]

rotate 2 steps to the right: 
[6,7,1,2,3,4,5]
rotate 3 steps to the right: 
[5,6,7,1,2,3,4]

Example 2:

Input: 
[-1,-100,3,99]
 and k = 2
Output: [3,99,-1,-100]
Explanation: 
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]

Note:

• Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
• Could you do it in-place with O(1) extra space?

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<思路>这个题直接用python的list切片就行。注意先要对list长度取余，防止循环次数大于list长度。

class Solution(object):
    def rotate(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: void Do not return anything, modify nums in-place instead.
        """
        k = k % len(nums)
        nums[:] = nums[-k:] + nums[:-k]