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

For example, with n = 7 and k = 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.
[show hint]

Hint:
Could you do it in-place with O(1) extra space?
Related problem: Reverse Words in a String II

Credits:

Special thanks to @Freezen for adding this problem and creating all test cases.

题意：翻转数组，k是要翻转多少遍。

java代码：

class Solution {
    public void rotate(int[] nums, int k) {  
        k %= nums.length;  
        reverse(nums, 0, nums.length - 1);  
        reverse(nums, 0, k - 1);  
        reverse(nums, k, nums.length - 1);  
    }  
    private void reverse(int[] nums, int m, int n) {  
        while (m < n) {  
            int temp = nums[m];  
            nums[m++] = nums[n];  
            nums[n--] = temp;  
        }  
    }  
}