Find the first element in a sorted array that is greater than the target

Question

In a general binary search, we are looking for a value which appears in the array. Sometimes, however, we need to find the first element which is either greater or less than

Answer 1

public static int search(int target, int[] arr) {
        if (arr == null || arr.length == 0)
            return -1;
        int lower = 0, higher = arr.length - 1, last = -1;
        while (lower <= higher) {
            int mid = lower + (higher - lower) / 2;
            if (target == arr[mid]) {
                last = mid;
                lower = mid + 1;
            } else if (target < arr[mid]) {
                higher = mid - 1;
            } else {
                lower = mid + 1;
       }
    }
    return (last > -1 && last < arr.length - 1) ? last + 1 : -1;
}

If we find 'target == arr[mid]', then any previous element would be either less than or equal to target. Hence, lower boundary is set as 'lower=mid+1'. Also, 'last' is the last index of 'target'. Finally we return 'last+1' - taking care of boundary conditions.