using System;

public class Program

{

    static int guess = 0;

    static Random rand = new Random(Guid.NewGuid().GetHashCode());

    static int min = 0;

    static int max = int.MaxValue;

    static int attempt = 0;

    public static void Main()

    {   

        int count = 0;

        int val = max;

        while ((val = (int)Math.Ceiling(val / 2d)) > 1) {

            //Console.WriteLine(val);

            count++;

        }

        Console.WriteLine("You have {0} attempts", count + 1);

        if (Guess(min, max, Verify) == guess)

            Console.WriteLine("YEY! Found it!");

    }

    public static int  Guess(int a, int b, Func<int, Result> CheckNumber) { 

        int half = b / 2;

        int n = half;

        Result r = Result.Unknown;

        while (Result.Correct != (r = CheckNumber(n)))

        {

            switch (r)

            {

                case Result.Bigger:

                    n += half = (int)Math.Ceiling(half / 2d);

                    break;

                case Result.Lower:

                    n -= half = (int)Math.Ceiling(half / 2d);

                    break;

            }

        }

        return n;

    }

    public static int  SecondGuess(int a, int b) {  

        int half = b / 2;

        int n = half;

        Result r = Result.Unknown;

        while (Result.Correct != (r = Verify(n)))

        {

            switch (r)

            {

                case Result.Bigger:

                    a = n;

                    n = rand.Next(a, b);

                    break;

                case Result.Lower:

                    b = n;

                    n = rand.Next(a, b);

                    break;

            }

        }

        return n;

    }

    public static Result Verify(int num) {

        if (guess == 0) 

            guess = rand.Next(min, max);

        attempt ++;

        Result res = Result.Correct;

        if (num < guess)

            res = Result.Bigger;

        else if (num > guess)

            res = Result.Lower;

        Console.WriteLine("Your attempt {2} of number {0} is {1}", num, res, attempt);

        return res;

    }

}

​

public enum Result 

{

    Bigger,

    Lower,

    Correct,

    Unknown

}