Random Array

RandomGenerator.cs

using System;
using System.Collections.Generic;
using System.Linq;
 
namespace TestConsole
{
    static class RandomGenerator
    {
        public static int[] KalladystineUniqueRandomNumbers(int min, int max, int howMany)
        {
            // check for impossible combinations
            if (howMany > max - min)
            {
                // throw new ArgumentException(String.Format("Range {0}-{1} is too small to have {2} unique random numbers.", min, max, howMany));
                Console.WriteLine(String.Format("Range {0}-{1} is too small to have {2} unique random numbers.", min, max, howMany));
                return null;
            }
 
            int[] myNumbers = new int[howMany];
 
            // special case for range and howMany being equal
            if (howMany == max - min)
            {
                // Linq version
                // return Enumerable.Range(min, howMany).ToArray();
 
                // for loop version
                for (int i = 0; i < howMany; i++)
                    myNumbers[i] = i;
                return myNumbers;
            }
 
            // actual generation of random numbers
            System.Random randNum = new System.Random();
            for (int currIndex = 0; currIndex < howMany; currIndex++)
            {
                // generate a candidate
                int randCandidate = randNum.Next(min, max);
 
                // generate a new candidate as long as we don't get one that isn't in the array
                while (myNumbers.Contains(randCandidate))
                {
                    randCandidate = randNum.Next(min, max);
                }
 
                myNumbers[currIndex] = randCandidate;
 
                // some optimizations
                if (randCandidate == min)
                    min++;
 
                if (randCandidate == max)
                    max--;
            }
 
            return myNumbers;
        }
 
        public static int[] BrathnannUniqueRandomNumbers(int min, int max, int howMany)
        {
            // check for impossible combinations
            if (howMany > max - min)
            {
                // throw new ArgumentException(String.Format("Range {0}-{1} is too small to have {2} unique random numbers.", min, max, howMany));
                Console.WriteLine(String.Format("Range {0}-{1} is too small to have {2} unique random numbers.", min, max, howMany));
                return null;
            }
 
 
            List<int> myList = new List<int>(howMany);
            for (int x = min; x < max; x++)
            {
                myList.Add(x);
            }
 
            // special case for range and howMany being equal
            if (howMany == max - min)
            {
                return myList.ToArray<int>();
            }
 
            System.Random rnd = new System.Random();
            var randomizedList = (from item in myList
                                  orderby rnd.Next()
                                  select item)
                                  .Take<int>(howMany).ToArray<int>();
            return randomizedList;
        }
    }
}