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

Solution:

1. 进行k次rotate，等效于进行 (k % nums.length)次rotate。
2. 借助reverse来实现rotate：rotate k次相当于将数组0到k-1的部分移动到数组k到length-1的后面，借助三次reverse可以达到这个效果。

public 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);
    }
    
    public void reverse(int[] nums, int start, int end)
    {
        while(start < end)
        {
            int temp = nums[start];
            nums[start] = nums[end];
            nums[end] = temp;
            start ++;
            end --;
        }
    }
}