189. Rotate Array

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

 

Given an array, rotate the array to the right by k steps, where k is non-negative.

Example 1:

Input: [1,2,3,4,5,6,7] and k = 3
Output: [5,6,7,1,2,3,4]
Explanation:
rotate 1 steps to the right: [7,1,2,3,4,5,6]
rotate 2 steps to the right: [6,7,1,2,3,4,5]
rotate 3 steps to the right: [5,6,7,1,2,3,4]

Example 2:

Input: [-1,-100,3,99] and k = 2
Output: [3,99,-1,-100]
Explanation: 
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]

Note:

• Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
• Could you do it in-place with O(1) extra space?