newton

using System;

namespace Newton
{
    class Program
    {
        static double EPSILON = 0.00001;

        static double func(double x)
        {
            return x *x - 4;
        }
        public static void Swap<T>(ref T a, ref T b)
        {
            T c = a;
            a = b;
            b = c;
        }

        static double deriveredFunc(double x)
        {
            double d = EPSILON / 100;
            return (func(x + d) - func(x)) / d;
        }
        static double f2p(double x)
        {
            double d = EPSILON / 100.0;
            return ((func(x + d) + func(x - d) - 2 * func(x)) / (d*d));
        }

        static void newtonRaphson(double a,double b)
        {
            double x = b;
            if (func(x) * f2p(x) < 0.0)
            {
                x = a;
            }
            int cnt = 0;
                double h = func(x) / deriveredFunc(x);
                while (Math.Abs(h) >= EPSILON)
                {
                cnt++;
                    h = func(x) / deriveredFunc(x);

                    x = x - h;
                }

                Console.WriteLine("The value of the"
                            + " root is : "
                            + Math.Round(x * 100.0) / 100.0);
            Console.WriteLine("cnt = " + cnt);


        }

        // Driver code
        public static void Main()
        {

            // Initial values assumed
            Console.WriteLine("Input a");
            double a = Convert.ToDouble(Console.ReadLine());
            Console.WriteLine("Input b");
            double b = Convert.ToDouble(Console.ReadLine());
            if (a > b)
            {
                Program.Swap(ref a, ref b);
            }
            newtonRaphson(a,b);
            Console.ReadLine();
        }
    }

}