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# Rotate Array

Rotate an array of n elements to the right by k steps.

For example, withn= 7 andk= 3, the array`[1,2,3,4,5,6,7]`is rotated to`[5,6,7,1,2,3,4]`.

**Note:**\
Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.

**Hint:**

Could you do it in-place with O(1) extra space?

Related problem:[Reverse Words in a String II](https://leetcode.com/problems/reverse-words-in-a-string-ii/)

三步翻转法

1. reverse the first n - k elements
2. reverse the rest of them
3. reverse the entire array

**O(n) in time, O(1) in space**

```
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.
        """
        l = len(nums)
        k = k % l
        self.reverse(nums, 0, l - k - 1)
        self.reverse(nums, l - k, l - 1)
        self.reverse(nums, 0, l - 1)

    def reverse(self, nums, start, end):
        while start < end:
            temp = nums[start]
            nums[start] = nums[end]
            nums[end] = temp
            start += 1
            end -= 1
```

剩下解法：

<https://discuss.leetcode.com/topic/47235/summary-of-solutions-in-python>

<http://bookshadow.com/weblog/2015/02/24/leetcode-rotate-array/>

For reversing the same list use:

```
array.reverse()    #Here array will be reversed in-place (no new list made)
```

To assign reversed list into some other list use:

```
newArray = array[::-1]
```