Urn Source Code 1

Urn Class, source code file Urn1.cs

/// <summary>
/// Simulate drawing balls from an urn (jar) without replacement.
/// Use a bool array to keep track of the balls.
/// </summary>

public class Urn
{
    // Private instance variables.
    private bool[] balls;
    private int _totalBalls;
    private Random r = new Random();

// Parameterized constructor.
    public Urn(int initialNumBalls)
    {
        // _totalBalls must be nonnegative.
        if (initialNumBalls > 0)
        {
            _totalBalls = initialNumBalls;
        }
        else
        {
            _totalBalls = 0;
        }

// Initialize array of balls.
        balls = new bool[_totalBalls + 1];
        for (int i = 0; i < _totalBalls; i++)
        {
            balls[i] = true;
        }
    }

// Public read-only method.
    public int TotalBalls
    {
        get { return _totalBalls; }
    }

// Public methods:

// Return number of balls remaining.
    public int BallsRemaining()
    {
        int count = 0;
        for (int i = 0; i < _totalBalls; i++)
        {
            if (balls[i])
            {
                count++;
            }
        }
        return count;
    }

// Return true if all entries 
    // in the balls array are false.
    public bool IsEmpty
    {
        get
        {
            for (int i = 0; i < _totalBalls; i++)
            {
                if (balls[i])
                {
                    return false;
                }
            }
            return true;
        }
    }

// Draw a ball from urn.
    public int Draw()
    {
        int n = r.Next(0, _totalBalls);

if (balls[n])
        {
            balls[n] = false;
            return n + 1;
        }
        else
        {
            for (int i = (n + 1) % _totalBalls; i != n;
                        i = (i + 1) % _totalBalls)
            {
                if (balls[i])
                {
                    balls[i] = false;
                    return i + 1;
                }
            }
            return -1;
        }
    }

// Print remaining balls in array.
    public override string ToString()
    {
        string b = "";
        for (int i = 0; i < _totalBalls; i++)
        {
            if (balls[i])
            {
                b += (i + 1).ToString() + " ";
            }
        }
        return "Remaining balls are " + b;
    }
}