Please see the general programming webpage for details about the programming environment for this course, guidelines for programming style, and details on electronic submission of assignments.

Collaboration Policy

For this assignment, you must work individually in regard to the design and implementation of your project.

Please make sure you adhere to the policies on academic integrity in this regard.

Contents:

• Overview
• Files We Are Providing
• File Format
• Input/Output in C++
• Files to Submit
• Grading Standards

Overview

You are to write a program that plays a game similar to "Twenty Questions." The user of the program will think of a secret item (e.g., Lisa) from a predetermined category (e.g., Simpson's Characters). The computer's tries to determine the secret by asking a series of yes/no questions such as Is the character a female? Internally, the computer relies upon a model known as a decision tree. As an example, here is a simple decision tree for Simpson's characters.

Notice that a given decision tree may be incomplete. For example, this particular tree does not include Lisa as a possible answer. In this case, the computer's algorithm will not succeed, but we can use that failure to further adapt the decision tree. We use a simple model for "learning" based on expert advice. As an example, here is a possible round of our game (user's responses shown in bold):

The category is Simpson's characters
Is the character female? Yes
Is the character an adult? No
Is your character Maggie? No
I give up.  What was your answer? Lisa
What would be a good question to help me distinguish between Maggie and Lisa?
Does the character play the saxophone?
For Lisa, would the proper answer to that question be Yes or No? Yes
Thank you.

Based upon this round, the updated decision tree would appear as:

Your goal is to write a complete program for playing rounds of such a game and for being able to save and load your internal decision tree as a data file. The overall flow of your program should offer the following menus. Upon start up, the program should offer:

Welcome. Please enter
  N    to start a new category
  L    to load an existing category

After the initial startup is complete and a new or existing tree has been loaded, the program should repeatedly offer the user the following options:

  P    to play a round of the game
  S    to save the current information to a file
  Q    to quit

Files We Are Providing

None!

We've provided many drivers and classes in past assignments. This time, we'll have you do it all. Although you might consider relying on the full-blown binary tree class from the textbook or lectures, we strongly recommend that you develop a simpler tree structure specifically for this assignment.

File Format

In order to save knowledge from one session to another, we want your program to be able to save/load a decision tree to/from an underlying text file. We require that you adhere to the following unambiguous file format.

• The first line of the file states the category.

• Each subsequent line of the file describes a single node of the decision tree, according to a pre-order traversal.
  • If the node is an internal node, the line of the file should be prefaced with Q: followed by a space and then the prose of the question.
  • If the node is an external node, the line of the file should be prefaced with A: followed by a space and then the respective answer for that node.

As an example, here is the precise file for our decision tree involving Simpson's characters.

Simpson's characters
Q: Is the character female?
Q: Is the character an adult?
A: Marge
Q: Does the character play the saxophone?
A: Lisa
A: Maggie
Q: Does the character ride a skateboard?
A: Bart
A: Homer

For your interest, we provide several larger decision tree that have been created by myself and past students.

• A more complete tree for Simpson's characters
• A decision tree for identifying models of cars
• A decision tree for identifying mammals
• A decision tree for identifying historical Kings and Queens of England

Input/Output in C++

Your program will need to deal with input and output from the user as well as from files. Fortunately, treatment of these two forms is quite similar due to the abstraction of a "stream" in C++. Standard I/O with the user is acommplished with the console streams cin and cout. Interactions with a file are accomplished with an instance of the fstream class.

Please note as well that we have designed the specifications for this project so that you can always read and write one line at a time. So for gathering input you should rely predominantly on the getline function.

Please refer to Ch. P.9 of the text and pages 15-16 of our Transition Guide for further discussion and examples about these I/O issues.

Files to Submit

Please submit the following:

• Your entire source code.

• One interesting decision tree that you have created and saved.

• A readme file provding a brief overview of your design.

Grading Standards

The assignment is worth 10 points.