calculate Pi using Monte Carlo

README.txt

This problem was asked by Google.

The area of a circle is defined as πr^2. 
Estimate π to 3 decimal places using a Monte Carlo method.

Hint: The basic equation of a circle is x2 + y2 = r2.

Program.cs

class Program
{
    static void Main(string[] args)
    {
        Tuple<long, double> tuple = CalculatePI(new Random(0));
        var points = tuple.Item1;
        var pi = tuple.Item2;
        Console.WriteLine($"PI: {pi} using Monte Carlo method with {points} points.");
    }

    private static Tuple<long, double> CalculatePI(Random rand)
    {
        long n = 0L;
        long insidePoints = 0L;
        do
        {
            n++;
            double x = rand.NextDouble();
            double y = rand.NextDouble();
            if (x * x + y * y <= 1.0)
            {
                insidePoints++;
            }
        } while (Math.Abs(Math.PI - insidePoints * 4.0 / n) > 1e-3);
        return new Tuple<long, double>(n, insidePoints * 4.0 / n);
    }
}