20 Questions
Assignment Intro
James Wei
Professor Peck
March 19, 2014
Slides by James Wei
Outline
• A look at the game of 20Q
• Classes of 20Q/Model-View design
• Implementation
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Reading a file
Building a tree
Playing the game
Adding to the tree
Saving a file
A look at 20Q
• We want to create a simplified version of 20Q
• Here are the features we implement:
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Can play 20Q
Can create game trees from files
Can improve tree when computer loses
Can save improved game trees to files
• Sample playthrough
Classes of 20Q
• The classes of 20Q:
• GameMain – runs 20Q
• IAnimalModel – defines the methods and
behaviors available to the model
• AnimalGameModel – implements IAnimalModel
• AnimalGameViewer – handles display logic
• AnimalNode – represents a node on the tree
• WebGameInfo – don’t worry about this one
Model-View Design
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Code is split between model and view
You write the model
Know how to interact with the view
Nothing new here…
Model-View Design
Implementation -- Overview
• A few parts to this assignment:
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Reading a file: initialize()
Building a tree: initialize()
Playing the game: newGame(), processYesNo()
Adding to the tree: addNewQuestion(),
addNewKnowledge()
• Saving a file: write()
• Also consider while you’re coding—what
instance variables do we need in the model?
Implementation -- Overview
• View methods you will need to use:
• void update(String) – displays text in main pane
• void showMessage(String) – displays text in
message pane
• void showDialog(String) – displays a popup with
the given text
• void getNewInfoLeaf() – tells view to ask for a
new tree leaf
• void getDifferentiator() – tells view to ask for a
new question node
Implementation -- Overview
Implementation – File I/O
• Reading a file
• Need to start by building the 20Q tree from a file
• Implement this method:
void initialize(Scanner)
• initialize must do the following:
• Use the scanner to read the file line by line
• Use each line to build one node of the tree (in preorder)
• Strip the “#Q:” from each question before creating its
internal node
• Call myView.setEnabled(true)
• Call newGame() at the very end to start a game
Implementation – File I/O
Implementation – File I/O
• Your life will be much easier if you write a
recursive helper method
• Some pseudo-code to get you started:
private AnimalNode readHelper(Scanner s)
{
String line = s.nextLine();
if (line is leaf) {
// create new leaf
}
// recursively create left (yes) subtree
// recursively create right (no) subtree
// create internal node from subtrees
}
Implementation – File I/O
• Writing a file
• Need to be able to save trees to file
• Implement this method:
void write(FileWriter)
• write must do the following:
• Write one line in the file for each node using the
FileWriter write() method
• Write a preorder traversal
• Prepend “#Q:” for each question (internal node)
• Append “\n” to the end of each line to signify new line
Implementation -- Overview
• A few parts to this assignment:
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•
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Reading a file: initialize()
Building a tree: initialize()
Playing the game: newGame(), processYesNo()
Adding to the tree: processYesNo(),
addNewQuestion(), addNewKnowledge()
• Saving a file: write()
Implementation – Playing 20Q
• Playing the game
• Begins when the player clicks “New Game”, or
when the player loads a file, both of which call
the model method newGame()
• First implement this method:
void newGame()
• newGame must do the following:
• Set all instance variables to their initial state
• Ask the first question
Implementation – Playing 20Q
• Playing the game
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As you ask questions, the user responds with YES or
NO by clicking a button in the view—those buttons
call processYesNo(boolean)
Next implement this method:
void processYesNo(boolean)
processYesNo must do the following:
• Update the current position on the game tree according to
the user’s response
• Ask the next question – remember this varies depending on
if we are at an internal or a leaf!
• Display a WIN or LOSE message if game has ended
• Few more things which we’ll discuss in the next part…
Implementation -- Overview
• A few parts to this assignment:
•
•
•
•
Reading a file: initialize()
Building a tree: initialize()
Playing the game: newGame(), processYesNo()
Adding to the tree: processYesNo(),
addNewQuestion(), addNewKnowledge()
• Saving a file: write()
Implementation – Improving
• Improving the tree
• If the computer loses, it’s time to add to our tree!
• Go back and add to this method:
void processYesNo(boolean)
• processYesNo must also do the following:
• Ask for the answer (what were you thinking of?)
• Call getNewInfoLeaf() – this will tell the view to
popup a dialog box where the user can type a response
Implementation – Improving
• Improving the tree
• getNewInfoLeaf will call another model method
• Implement this method:
void addNewQuestion(String)
• addNewQuestion must do the following:
• Display a list of all of the user’s answers up to that
point, e.g. “You answered YES to <QUESTION>, You
answered NO to <QUESTION>, etc.”
• Create a new leaf node for the correct answer
• Ask for a differentiator question
• Call getDifferentiator()
Implementation – Improving
• Improving the tree
• addNewQuestion will call the final method
• Implement this method:
void addNewKnowledge(String)
• addNewKnowledge must do the following:
• Create a new internal node for the differentiator
• Set the differentiator’s YES answer to the existing,
incorrect answer that the computer guessed, and the
differentiator’s NO answer to the new, correct answer
• Add the internal node to the game tree
• Start a new game
Implementation – Improving
• Example – here’s the tree before playing:
For reference ->
Implementation – Improving
• Example – here’s the tree after playing:
For reference ->
Wrapping Up
• So you slept through this whole thing and now
you just want to know what to do, eh?
• My recommended course of action:
• Implement file I/O, aka initialize() and write()
• Test by opening a file and saving it
• Implement newGame() and processYesNo(),
leaving out improving the tree for now
• Play the game – try winning and losing
• Implement addNewQuestion() and
addNewKnowledge()
• Test it – open a file, play several times (win/lose),
improve the tree, play with new tree, save file
Good luck!
I didn’t have time to find a witty tree
or 20Q related cartoon… 