20 Questions Guessing Game using Binary Trees

Finishing the game

The binary tree is now programmed and it is time to put the finishing details on the project. When the game starts we need to create a new binary tree to hold the computer's knowledge. A new game needs one question and two objects and is executed in the startNewGame() method. Add the following code to the file which contains your main method.

Starting a New Game

static void startNewGame()
{
    Console.WriteLine("No previous knowledge found!");
    Console.WriteLine("Initializing a new game.\n");
    Console.WriteLine("Enter a question about an object: ");
    string question = Console.ReadLine();
    Console.Write("Enter a guess if the response is Yes: ");
    string yesGuess = Console.ReadLine();
    Console.Write("Enter a guess if the response is No: ");
    string noGuess = Console.ReadLine();
    tree = new BTTree(question, yesGuess, noGuess);
}

The startNewGame method needs to be called by the Main() method. Change the current Main() method to the following. After you add the following code you will be able to run one game.

Adding the ability to play one game

static void Main(string[] args)
{
    startNewGame();
    Console.WriteLine("\nStarting the Game");
    tree.query(); //play one game
}

Making a Play Again Option

This is not a useful game if we can only play one round. We need to add a play again option. Add the following method to the file that contains the Main() method. This method returns true if the user wants to play again, else false.

Adding the ability to play one game

static bool playAgain()
{
    Console.Write("\nPlay Another Game? ");
    char inputCharacter = Console.ReadLine().ElementAt(0);
    inputCharacter = Char.ToLower(inputCharacter);
    while (inputCharacter != 'y' && inputCharacter != 'n')
    {
        Console.WriteLine("Incorrect input please enter again: ");
        inputCharacter = Console.ReadLine().ElementAt(0);
        inputCharacter = Char.ToLower(inputCharacter);
    }
    if (inputCharacter == 'y')
        return true;
    else
        return false;
}

Change your main function to the following and enjoy playing your game. Please feel free to contact me if you have any questions. My email is located at the top of this lesson.

Adding the ability to play one game

static void Main(string[] args)
{
    startNewGame();
    Console.WriteLine("\nStarting the Game");
    tree.query(); //play one game
    while(playAgain())
    {
        Console.WriteLine();
        tree.query(); //play one game
    }
}

Complete Code Files

BTNode.cs

The Complete BTNode.cs Class File

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace MCS_Week_001
{
    [Serializable] class BTNode
    {
        string message;
        BTNode noNode;
        BTNode yesNode;
        /**
         * Constructor for the nodes: This class holds an String representing
         * an object if the noNode and yesNode are null and a question if the
         * yesNode and noNode point to a BTNode.
         */
        public BTNode(string nodeMessage)
        {
            message = nodeMessage;
            noNode = null;
            yesNode = null;
        }
        public void query()
        {
            if (this.isQuestion())
            {
                Console.WriteLine(this.message);
                Console.Write("Enter 'y' for yes and 'n' for no: ");
                char input = getYesOrNo(); //y or n
                if (input == 'y')
                    yesNode.query();
                else
                    noNode.query();
            }
            else
                this.onQueryObject();
        }
        public void onQueryObject()
        {
            Console.WriteLine("Are you thinking of a(n) " + this.message + "?");
            Console.Write("Enter 'y' for yes and 'n' for no: ");
            char input = getYesOrNo(); //y or n
            if (input == 'y')
                Console.Write("The Computer Wins\n");
            else
                updateTree();
        }
        private void updateTree()
        {
            Console.Write("You win! What were you thinking of?");
            string userObject = Console.ReadLine();
            Console.Write("Please enter a question to distinguish a(n) "
                + this.message + " from " + userObject + ": ");
            string userQuestion = Console.ReadLine();
            Console.Write("If you were thinking of a(n) " + userObject
                + ", what would the answer to that question be?");
            char input = getYesOrNo(); //y or n
            if (input == 'y')
            {
                this.noNode = new BTNode(this.message);
                this.yesNode = new BTNode(userObject);
            }
            else
            {
                this.yesNode = new BTNode(this.message);
                this.noNode = new BTNode(userObject);
            }
            Console.Write("Thank you my knowledge has been increased");
            this.setMessage(userQuestion);
        }
        public bool isQuestion()
        {
            if (noNode == null && yesNode == null)
                return false;
            else
                return true;
        }
        /**
         * Asks a user for yes or no and keeps prompting them until the key
         * Y,y,N,or n is entered
         */
        private char getYesOrNo()
        {
            char inputCharacter = ' ';
            while (inputCharacter != 'y' && inputCharacter != 'n')
            {
                inputCharacter = Console.ReadLine().ElementAt(0);
                inputCharacter = Char.ToLower(inputCharacter);
            }
            return inputCharacter;
        }
        //Mutator Methods
        public void setMessage(string nodeMessage)
        {
            message = nodeMessage;
        }
        public string getMessage()
        {
            return message;
        }
        public void setNoNode(BTNode node)
        {
            noNode = node;
        }
        public BTNode getNoNode()
        {
            return noNode;
        }
        public void setYesNode(BTNode node)
        {
            yesNode = node;
        }
        public BTNode getYesNode()
        {
            return yesNode;
        }
    }
}

BTTree.cs

The Complete BTTree.cs Class File

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace MCS_Week_001
{
    class BTTree
    {
        BTNode rootNode;
        public BTTree(string question, string yesGuess, string noGuess)
        {
            rootNode = new BTNode(question);
            rootNode.setYesNode(new BTNode(yesGuess));
            rootNode.setNoNode(new BTNode(noGuess));
        }
        public void query()
        {
            rootNode.query();
        }
    }
}

Program.cs (Main() Method file)

The Complete Main() Method file

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;

namespace MCS_Week_001
{
    class Program
    {
        static BTTree tree;
        static void Main(string[] args)
        {
            startNewGame();
            Console.WriteLine("\nStarting the Game");
            tree.query(); //play one game
            while(playAgain())
            {
                Console.WriteLine();
                tree.query(); //play one game
            }
        }
        static bool playAgain()
        {
            Console.Write("\nPlay Another Game? ");
            char inputCharacter = Console.ReadLine().ElementAt(0);
            inputCharacter = Char.ToLower(inputCharacter);
            while (inputCharacter != 'y' && inputCharacter != 'n')
            {
                Console.WriteLine("Incorrect input please enter again: ");
                inputCharacter = Console.ReadLine().ElementAt(0);
                inputCharacter = Char.ToLower(inputCharacter);
            }
            if (inputCharacter == 'y')
                return true;
            else
                return false;
        }
        static void startNewGame()
        {
            Console.WriteLine("No previous knowledge found!");
            Console.WriteLine("Initializing a new game.\n");
            Console.WriteLine("Enter a question about an object: ");
            string question = Console.ReadLine();
            Console.Write("Enter a guess if the response is Yes: ");
            string yesGuess = Console.ReadLine();
            Console.Write("Enter a guess if the response is No: ");
            string noGuess = Console.ReadLine();
            tree = new BTTree(question, yesGuess, noGuess);
        }
    }
}