OrderAgnosticBS.java

public class OrderAgnosticBS {
    public static void main(String[] args) {
//        int[] arr = {-18, -12, -4, 0, 2, 3, 4, 15, 16, 18, 22, 45, 89};
        int [] arr = {99, 80, 75, 22, 11, 10, 5, 2, -3};
        int ans = orderAgnosticBS(arr,22 );
        System.out.println(ans);
    }

    static int orderAgnosticBS(int[] arr, int target){
        int start=0;
        int end=arr.length-1;

        // find whether the array is sorted in ascending or descending
        boolean isAsc = arr[start]< arr[end];


        while(start<=end){
            // find the middle element
//            int mid = (start +end)/2;  // might be possible that (start+end) exceeds the range of int in java
            int mid = start + (end-start)/2;

            if (arr[mid]== target){
                return mid;
            }
            if(isAsc) {
                if (target < arr[mid]) {
                    end = mid - 1;
                } else if (target > arr[mid]) {
                    start = mid + 1;
                }
            }
            else{
                if (target > arr[mid]) {
                    end = mid - 1;
                } else if (target < arr[mid]) {
                    start = mid + 1;
                }
            }
        }
        return -1;
    }
}