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C#-Quelltext

int RandomChoice(double[] probabilities)
{
    // Die Summe der Werte in "probabilities" muss 1 sein!
    
    double p = 0;
    double r = RandomNumberBetweenZeroAndOne();
    for (int i = 0; i < probabilities.Length - 1; ++i)
        if (r < (p += probabilities[i])) return i;
    
    return probabilities.Length - 1;
}

C#-Quelltext

using System;

namespace RandomTest
{
    class Program
    {
        private static Random rng = new Random();

        private static int RandomChoice(double[] probabilities)
        {
            // Die Summe der Werte in "probabilities" muss 1 sein!

            double p = 0;
            double r = rng.NextDouble();
            for (int i = 0; i < probabilities.Length - 1; ++i)
                if (r < (p += probabilities[i])) return i;

            return probabilities.Length - 1;
        }

        private static void Main(string[] args)
        {
            double[] probabilities = { 0.3, 0.4, 0.2, 0.05, 0.05 };
            int numSamples = 100000000;

            int[] count = new int[probabilities.Length];
            for (int i = 0; i < numSamples; ++i)
                ++count[RandomChoice(probabilities)];

            foreach (int n in count)
                Console.WriteLine((double)n / numSamples);
        }
    }
}

Quellcode

0,30000489
0,40006654
0,19993
0,05001256
0,04998601