NP138 Random

Question

Hi Guys

NP138 Random

In the following program output 1, 2, 3, 4, 5 and 6 is coming, 7 is not coming. Please explain the reason.

Thank you

using System;

class MainClass

{

public static void Main()

{

Random ran = new Random();

Console.WriteLine(ran.Next(1, 7));

}

Alan · Answer

It's because the Random.Next(a b) method produces a random integer 'x' in the range a In other words the start point is included but the endpoint is not. Not sure why it was done this way but it's a point you need to be careful about in practice.

Maha · Answer

Thank you very much for explanation.

Alan · Answer

The r2.Next(150000) call produces a random integer 'i' in the range: 0 so 75274 is within that range. The r2.NextDouble() call produces a random double 'd' in the range: 0 so 0.571986661558965 is within that range.

Maha · Answer

Thank you for explanation. How this can be explained? Console .WriteLine(r2.Next(150000)); //75274 Console .WriteLine(r2.NextDouble()); //0.571986661558965

Alan · Answer

The number passed to the Random constructor is what's called a 'seed' value. This is simply a starting value from which the pseudo-random sequence of random numbers will be generated - it is nothing to do with the range of those numbers. So in the first example calling Random.Next() without an argument can produce any random integer between 0 and int.MaxValue - 1 (2147483646) inclusive. The number produced (214873035) is of course well within that range.

Maha · Answer

How can output of the following program be explained? Note that Random ( ) constructor is holding a number 99830123. using System; //using System.Collections.Generic; //using System.Globalization; //using System.IO; //using System.Text; public class MainClass { public static void Main() { Random r2 = new Random (99830123); Console .WriteLine(r2.Next()); //214873035 Console .WriteLine(r2.Next(150000)); //75274 Console .WriteLine(r2.Next(9999 100750)); //85587 Console .WriteLine(r2.NextDouble()); //0.571986661558965 } }