sorted search increase performance

Question

Running through exercises on testdome...currently looking at https://www.testdome.com/for-developers/solve-question/9877

Implement function CountNum

Answer 1

They expect you to use the Array.BinarySearch method to get 100%.

using System;

public class SortedSearch
{
    public static int CountNumbers(int[] sortedArray, int lessThan)
    {
        int lengthOfArray = sortedArray.Length;
        if (lengthOfArray == 0) return 0;

        if (sortedArray[0] >= lessThan) return 0;
        if (sortedArray[lengthOfArray - 1] < lessThan) return lengthOfArray;

        int index = Array.BinarySearch(sortedArray, lessThan);
        if (index < 0)
            return ~index;

        return index;
    }

    public static void Main(string[] args)
    {
        Console.WriteLine(SortedSearch.CountNumbers(new int[] { 1, 3, 5, 7 }, 4));
    }
}