Question

I was trying to implement an extension of Random class.

But this function will have one feature, you can get a number followed step. For example:

RandNumb(double min, double max, double step)
RandNumb(1, 10, 2) = 6
RandNumb(100, 1000, 500) = 1000
RandNumb(0.001, 0.1, 0.01) = 0.15

My first idea was to get a random number from min to max, and compare if this is a valid number (because of the step). If not, again generate another number.

But I’m sure that this is not a good performance. What do you think?

Answer 1

By definition of the problem, it seems that the valid values ​​for “RandNumb (1, 10, 2)” would be: 1, 3, 5, 7, 9.

In that case. The code would look like:

class Program
{
    static void Main(string[] args)
    {
        Random rd = new Random();
        for (int i = 0; i < 10; i++)
        {
            Console.WriteLine("RandNumb(rd, 1, 10, 2)=" + RandNumb(rd, 1, 10, 2));
            Console.WriteLine("RandNumb(rd, 100, 1000, 500)=" + RandNumb(rd, 100, 1000, 500));
            Console.WriteLine("RandNumb(rd, 0.001, 0.1, 0.01) =" + RandNumb(rd, 0.001, 0.1, 0.01)); 
        }
        Console.ReadLine();
    }

    public static double RandNumb(Random rd, double min, double max, double step)
    {
        int range = (int)Math.Floor((max - min) / step);
        int stepCount = rd.Next(0, range + 1);
        return min + (step * stepCount);
    }
}

And the result would look like this:

RandNumb(rd, 1, 10, 2)=3
RandNumb(rd, 100, 1000, 500)=600
RandNumb(rd, 0.001, 0.1, 0.01) =0,071
RandNumb(rd, 1, 10, 2)=5
RandNumb(rd, 100, 1000, 500)=600
RandNumb(rd, 0.001, 0.1, 0.01) =0,041
RandNumb(rd, 1, 10, 2)=3
RandNumb(rd, 100, 1000, 500)=600
RandNumb(rd, 0.001, 0.1, 0.01) =0,081
RandNumb(rd, 1, 10, 2)=9
RandNumb(rd, 100, 1000, 500)=600
RandNumb(rd, 0.001, 0.1, 0.01) =0,011
RandNumb(rd, 1, 10, 2)=7
RandNumb(rd, 100, 1000, 500)=100
RandNumb(rd, 0.001, 0.1, 0.01) =0,091
RandNumb(rd, 1, 10, 2)=5
RandNumb(rd, 100, 1000, 500)=100
RandNumb(rd, 0.001, 0.1, 0.01) =0,001
RandNumb(rd, 1, 10, 2)=1
RandNumb(rd, 100, 1000, 500)=600
RandNumb(rd, 0.001, 0.1, 0.01) =0,071
RandNumb(rd, 1, 10, 2)=1
RandNumb(rd, 100, 1000, 500)=600
RandNumb(rd, 0.001, 0.1, 0.01) =0,061
RandNumb(rd, 1, 10, 2)=5
RandNumb(rd, 100, 1000, 500)=100
RandNumb(rd, 0.001, 0.1, 0.01) =0,041
RandNumb(rd, 1, 10, 2)=3
RandNumb(rd, 100, 1000, 500)=600
RandNumb(rd, 0.001, 0.1, 0.01) =0,021