189. Rotate Array

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?

//先将5以前的数据翻转得到的数组是[4,3,2,1,5,6,7]
//再将5及以后的数据翻转得到的数组是[4,3,2,1,7,6,5]
//再将整个数组翻转即得到[5,6,7,1,2,3,4]. （即为所求）
// while(i < j && i >= 0) 如果没有了等于0则会变得2个元素的时候不通过

public class Solution {
    public void rotate(int[] nums, int k) {
        int len = nums.length;
        k = k % len;
        if(nums.length == 1){
            return;
        }
        if(k == 0){
            return;
        }
        reverse(nums, 0, len - 1 - k);
        reverse(nums, len - k, len - 1);       
        reverse(nums, 0, len - 1);
    }
    public void reverse(int[] nums, int i, int j){
        while(i < j && i >= 0){
            int temp = 0;
            temp = nums[j];
            nums[j] = nums[i];
            nums[i] = temp;
            i++;
            j--;
        }
    }
}