countRotationsInArray.java

public class countRotationsInArray {
//    https://www.geeksforgeeks.org/find-rotation-count-rotated-sorted-array/
    public static void main(String[] args) {
        int[] arr = {4, 5, 6, 7, 8, 0, 1, 2};
        System.out.println(countRotations(arr));
    }
    static int countRotations(int[] arr)
    {
        int pivot = peak(arr);
        return pivot+1;
    }

    static int peak(int[] arr)
    {
        int start = 0;
        int end = arr.length-1;
        while(start <= end)
        {
            int mid = start + (end - start)/2;
            if(mid < end && arr[mid] > arr[mid+1])
            {
                return mid;
            }
            if(start < mid && arr[mid] < arr[mid-1])
            {
                return mid-1;
            }
            if(arr[mid] <= arr[start])
            {
                end = mid - 1;
            }
            else
            {
                start = mid + 1;
            }
        }
        return -1;
    }
}