How Can I create Random Numbers?

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How can I create 4-digit Random Numbers? without use Structural Loops and Structural condition (for example Loop for,while,if,...) and without use from Timer
result of this program like this program:

4-digit Produced Must different for example if return 1111 is false. but result 1234 is true.

C#

static void Main(string[] args)
       {
           Random Item = new Random();

           int Num1, Num2, Num3, Num4;
           do
           {
               Num1 = Item.Next(0, 10);
               Num2 = Item.Next(0, 10);
               Num3 = Item.Next(0, 10);
               Num4 = Item.Next(0, 10);

           } while (Num1 == Num2 || Num1 == Num3 || Num1 == Num4 || Num2 == Num3 || Num2 == Num4 || Num3 == Num4);

           Console.WriteLine("{0}{1}{2}{3}", Num1, Num2, Num3, Num4);
           Console.ReadKey();
       }

Posted 22-Dec-15 9:56am

z@hr@

Updated 23-Dec-15 4:51am

v5

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Sergey Alexandrovich Kryukov 22-Dec-15 16:03pm

What's wrong with just reading original MSDN documentation?
—SA

BillWoodruff 23-Dec-15 2:22am

"without loops" ... that does not make much sense, and you need to clarify what this is about.

Philippe Mori 25-Dec-15 20:22pm

Having a loop like that might not be very efficient as you would loop a few time with same digits... In that case, this should not be much of a problem since you pick only 4 digits among 10. However, if you would pick 90 distinct 2 digits number, the would be a lot of iteration most of the time. You can do some statistics to have an idea of the average number of iteration... or try the function a few thousand time and count the number of iterations. In most case, it might lead to (almost) infinite loop if the probability of getting a sequence without repeating number is too low...

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Sergey Alexandrovich Kryukov · Accepted Answer · 2015-12-22T10:10:00

Please see: https://msdn.microsoft.com/en-us/library/system.random%28v=vs.110%29.aspx[^].

Don't make a common mistake, creating the instance of System.Random several times. Remember, the algorithm pseudo-randon. To randomize of, always use the seed:
https://msdn.microsoft.com/en-us/library/ctssatww%28v=vs.110%29.aspx[^].

As you can see from the code sample shown in the article referenced above, you can use System.DateTime.Now for seeding. To understand why seeding is needed and how pseudo-random algorithm gives you random numbers, please see: https://en.wikipedia.org/wiki/Pseudorandom_number_generator[^].

After you create your instance of System.Random, reuse it for all your needs, just one instance. In your case, all other calls should be to System.Random(int, int):
https://msdn.microsoft.com/en-us/library/2dx6wyd4(v=vs.110).aspx[^].

[EDIT]

Warning! The parameter names are really misleading. minValue is really the minimum, but maxValue is not really maximum; the documentation calls it "exclusive upper bound", which means that real maximum is maxValue − 1. :-)
See also the notes in Return value section.

[END EDIT]

Your "without loops" is simply an absurd. Okay, code the calls to Random.Next 100 times to get 100 numbers, but I doubt anyone would be so insane.

—SA

Philippe Mori · Accepted Answer · 2015-12-25T14:17:00

With something like that, you don't have any "visible" loop or condition (assuming, you want to generate a single 4 digits number):

C#

class FourRandomDigits
{
	public static string Run()
	{
	    var generator = new FourRandomDigits();
	    return generator.DoRun();
	}

        private static Random rand = new Random();
	private int[] digits = new int[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
	private int remainingCount = 10;
	
	private string DoRun()
	{
	    var builder = new StringBuilder();
	    builder.Append(PickOneDigit());
	    builder.Append(PickOneDigit());
	    builder.Append(PickOneDigit());
	    builder.Append(PickOneDigit());
	    return builder.ToString();
	}
	
	private int PickOneDigit()
	{
	    int index = rand.Next(remainingCount);
	    int result = digits[index];
	    digits[index] = digits[--remainingCount];
	    return result;
	}
}

How Can I create Random Numbers?

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