class Solution {
    public void reverse(int[] nums, int i, int j)
    {
        while(i<=j)
        {
            int temp = nums[i];
            nums[i] = nums[j];
            nums[j] = temp;
            i++;
            j--;
        }
    }
    public void rotate(int[] nums, int k) {
        int n = nums.length;
        k = k%n;
        // rotate first whole array
        reverse(nums,0,n-1); // [7,6,5,4,3,2,1]
        // rotate first k elements
        reverse(nums,0,k-1); // [5,6,7,4,3,2,1]
        // rotate from kth element to last
        reverse(nums,k,n-1); // [5,6,7,1,2,3,4]
    }
}