Generating Random Numbers Without Repeating.C#

Generating random numbers without repeating.C#

Check each number that you generate against the previous numbers:

List<int> listNumbers = new List<int>();
int number;
for (int i = 0; i < 6; i++)
{
  do {
     number = rand.Next(1, 49);
  } while (listNumbers.Contains(number));
  listNumbers.Add(number);
}

Another approach is to create a list of possible numbers, and remove numbers that you pick from the list:

List<int> possible = Enumerable.Range(1, 48).ToList();
List<int> listNumbers = new List<int>();
for (int i = 0; i < 6; i++)
{
  int index = rand.Next(0, possible.Count);
  listNumbers.Add(possible[index]);
  possible.RemoveAt(index);
}

How can i generate random numbers without repeating/duplicate the same number?

First of make only one instance of Random, and then use a list to store all generated numbers and check it before creating files with the newly generated number

Random rnd = new Random();
List<long> generatedNumbers = new List<long>();
for (int i = 0; i < numberoffiles; i++)
{
    long rndsize = rnd.Next(1, 2000);
    if(generatedNumbers.Contains(rndSize)) 
    {
      i--;
      continue;
    }

    generatedNumbers.Add(rndSize);
    FileStream fs = new FileStream(@"c:\temp\files\huge_dummy_file" + i, FileMode.CreateNew);
    fs.Seek(rndsize * 1024, SeekOrigin.Begin);
    fs.WriteByte(0);
    fs.Close();
}

How can I create a List of random int numbers without repeating?

Or use LINQ. (By generating a sequence between Min and Max with Enumerable.Range):

var rnd = new Random();
var res = Enumerable.Range(Min, Max - Min + 1).OrderBy(x => rnd.Next()).ToList();

And if you want to pick specific number of the sequence you can use Take method. Like this:

var res = Enumerable.Range(Min, Max - Min + 1).OrderBy(x => rnd.Next()).Take(5).ToList();

Generating random numbers without repeating.C#

Check each number that you generate against the previous numbers:

List<int> listNumbers = new List<int>();
int number;
for (int i = 0; i < 6; i++)
{
  do {
     number = rand.Next(1, 49);
  } while (listNumbers.Contains(number));
  listNumbers.Add(number);
}

Another approach is to create a list of possible numbers, and remove numbers that you pick from the list:

List<int> possible = Enumerable.Range(1, 48).ToList();
List<int> listNumbers = new List<int>();
for (int i = 0; i < 6; i++)
{
  int index = rand.Next(0, possible.Count);
  listNumbers.Add(possible[index]);
  possible.RemoveAt(index);
}

Generate non duplicate random number

You can use a recursive function to do this:

    private static List<int> GetRandomRow(List<int> row, int colCount, int min, int max)
    {
        if(colCount <= 0)
        {
           return row;
        }

        var next = rnd.Next(min, max);
        if(row.Contains(next))
        {
           return GetRandomRow(row, colCount, min, max);
        }

        row.Add(next);

        return GetRandomRow(row, colCount - 1, min, max);
     }

Then you can use your program like:

    private static Random rnd = new Random();

    static void Main(string[] args)
    {
        int min = 0; // minimum number
        int max = 36; // maximum number
        int rows = 10; // number of rows in my copun
        int col = 7; // number of column in my copun

        // Get the date of PC
        string NameDate;
        NameDate = DateTime.Now.ToString("yyyy.MM.dd");
        string Week = "1-uge";
        string ComName = "LYN LOTTO";
        Random rnd = new Random();

        Console.WriteLine("{0,22} \n {1,15} \n{2,18}", NameDate, Week, ComName);
        for (int i = 0; i < rows; i++)
        {
            Console.Write($"{i + 1}.");

            var row = new List<int>();
            var currentRow = GetRandomRow(row, col, min, max);
            foreach (var currentCol in currentRow)
            {
                Console.Write("{1,4}", i, currentCol);
            }

            Console.WriteLine();
         }

         Console.WriteLine("***** JOKER TAL *****");
         for (int i = 0; i < 2; i++)
         {
             for (int j = 0; j < col; j++)
                 Console.Write("{0,4}", rnd.Next(1, 9));
             Console.WriteLine();
         }
      }

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