using System;

public class Program

{

    public static void Main()

    {

        int coins = 50;

        Console.WriteLine("Welcome to the Monty Hall game!");

        while (coins >= 10)

            coins = Play(coins);

​

    }

​

    static int Play(int coins)

    {

        Random rnd = new Random();

        double cost =  (Math.Floor(coins/ 100.0) * 10.0) + 10;

        int[] doors = { 0, 0, 0 };

        double prize = Math.Floor((coins + cost) / 5.0) * 5.0;

        doors[rnd.Next(0, 3)] = 1;

        int removedDoor = rnd.Next(0, 3);

        int otherDoor = 0;

        Console.WriteLine("You currently have " + coins + " coins.");

        Console.WriteLine("There are three doors, behind one is " + prize + " coins.");

        Console.WriteLine("Would you like to play a round of the game, it will cost you " + cost + " coins. (Y/N)");

        if (!(YesOrNo()))

        {

            Console.WriteLine("Thank you for playing, your end score is : " + coins + ".");

            return 0;

        }

        coins -= Convert.ToInt32(cost);

        Console.WriteLine("Which door do you think the prize is behind? (1/2/3)");

        int guess = NumericalInput(1, 3) - 1;

​

        while ((removedDoor == guess) | (doors[removedDoor] == 1))

            removedDoor = rnd.Next(0, 3);

        while ((otherDoor == guess) | (otherDoor == removedDoor))

            otherDoor++;

​

        Console.WriteLine("The host has opened door " + (removedDoor + 1) + ", behind it was nothing. ");

        Console.WriteLine("Would you like to swap to door " + (otherDoor + 1) + "? (Y/N)");

        if (YesOrNo())

            guess = otherDoor;

​

        if (doors[guess] == 1)

        {

            Console.WriteLine("You have won the " + prize + " coins prize!");

            Console.WriteLine("");

            return coins + Convert.ToInt32(prize);

        }

        else

        {

            Console.WriteLine("There was nothing behind the door, better luck next time.");

            Console.WriteLine("");

            return coins;

        }

    }

​

    static bool YesOrNo()

    {

        while (true)

        {

            string response = Console.ReadLine().ToLower();

            if (response.Length > 0)

            {

                if (response[0] == Convert.ToChar("n"))

                    return false;

                else if (response[0] == Convert.ToChar("y"))

                    return true;

            }

​

            Console.WriteLine("You did not enter Yes or No. Try again:");

        }

    }

​

    static int NumericalInput(int start, int options)

    {

        // Validates if the user has entered a number a number corresponding to an option 

        string[] numWords =

        {"zero", "one", "two", "three", "four"};

        string response;

        int responseNum;

        int position;

        while (true)

        {

            response = Console.ReadLine().ToLower();

            if (response.Length > 0)

            {

                if (ValidNumber(response))

                {

                    responseNum = Convert.ToInt32(response);

                }

                else

                {

                    position = Array.IndexOf(numWords, response);

                    if (position > -1)

                    {

                        responseNum = position;

                    }

                    else

                        responseNum = options + 10;

                }

​

                if ((responseNum >= start) & (responseNum <= options))

                    return responseNum;

            }

            Console.WriteLine("You did not enter a number from " + start + " to " + options + ". Try again: ");

        }

    }

​

    static bool ValidNumber(string number)

    {

        // Checks if input is an integer

        for (int i = 0; i < number.Length; i++)

            if (char.IsDigit(number[i]) == false)

                return false;

        return true;

    }

}