using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static int GetDecimalsCount(decimal[] arrayToSearch, decimal[][] ranges)

    {

       if (arrayToSearch == null) throw new ArgumentNullException(nameof(arrayToSearch));

       if (ranges == null) throw new ArgumentNullException(nameof(ranges));

       if (ranges.Any(x =>x?.Length != 2)) throw new ArgumentException("Invalid ranges",nameof(ranges));

​

       var hashSet = new HashSet<decimal>();

​

       return arrayToSearch.Sum(item =>

             ranges.Any(range =>

                item >= range[0] &&

                item <= range[1]) ?1:0);

    }

​

    public static void Main()

    {

        decimal[] ArrayWithFiveElements = {0.1m, 0.2m, 0.3m, 0.4m, 0.5m};

        decimal[][] ranges = {new[]{0.1m, 0.2m}, new[]{0.4m, 0.5m}, new[]{decimal.Zero, decimal.One}, };

        Console.WriteLine(GetDecimalsCount(ArrayWithFiveElements, ranges));

    }

}