using System;

using System.Collections.Generic;

public class WeightedItem<T>

{

    private T value;

    private int weight;

    private int cumulativeSum;

    private static Random rndInst = new Random();

​

    public WeightedItem(T value, int weight)

    {

        this.value = value;

        this.weight = weight;

    }

​

    public static T Choose(List<WeightedItem<T>> items)

    {

        int cumulSum = 0;

        int cnt = items.Count();

​

        for (int slot = 0; slot < cnt; slot++)

        {

            cumulSum += items[slot].weight;

            items[slot].cumulativeSum = cumulSum;

        }

​

        double divSpot = rndInst.NextDouble() * cumulSum;

        WeightedItem<T> chosen =  items.FirstOrDefault(i => i.cumulativeSum >= divSpot);

        if (chosen == null) throw new Exception("No item chosen - there seems to be a problem with the probability distribution.");

        return chosen.value;

    }

    void program()

    {

        WeightedItem<string> alice = new WeightedItem<string>("alice", 1);

        WeightedItem<string> bob = new WeightedItem<string>("bob", 1);

        WeightedItem<string> charlie = new WeightedItem<string>("charlie", 1);

        WeightedItem<string> diana = new WeightedItem<string>("diana", 4);

        WeightedItem<string> elaine = new WeightedItem<string>("elaine", 1);

​

        List<WeightedItem<string>> myList = new List<WeightedItem<string>> { alice, bob, charlie, diana, elaine };

        string chosen = WeightedItem<string>.Choose(myList);

    }

}