189. Rotate Array java solutions

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.

public class Solution {
    public void rotate(int[] nums, int k) {
        int[] tmp = new int[k];
        int len = nums.length;
        k %= len;//处理k大于数组长度的情况
        for(int i = 0; i < k; i++){
            tmp[i] = nums[len-k+i];
        }
        len--;
        for(int i = len-k; i>= 0; i--){
            nums[len--] = nums[i];
        }
        for(int i = 0; i < k; i++){
            nums[i] = tmp[i];
        }
    }
}

解法二将数组0~len-1 逆置一次，0~k-1逆置一次，k~len-1逆置一次，即可得答案：

public class Solution {
    public void rotate(int[] nums, int k) {
        int len = nums.length;
        k %= len;
        reverse(nums,0,len-1);
        reverse(nums,0,k-1);
        reverse(nums,k,len-1);
    }
    
    public void reverse(int[] nums,int s, int e){
        while(s <= e){
            int tmp = nums[s];
            nums[s] = nums[e];
            nums[e] = tmp;
            s++;
            e--;
        }
    }
}