Trees - Data Structures and Abstractions with Java - page 583

FIGURE 23-17

The decision tree for a guessing game after acquiring another fact

Is it in North America?

No Ye s

Is it in Europe? U.S.A.

Ye s

No

Brazil England

LISTING 23-5

The class GuessingGame

import TreePackage.DecisionTreeInterface;
import TreePackage.DecisionTree;
public class GuessingGame
{

private DecisionTreeInterface<String> tree;

public GuessingGame(String question, String noAnswer, String yesAnswer)
{

DecisionTree<String> no = new DecisionTree<String>(noAnswer);
DecisionTree<String> yes = new DecisionTree<String>(yesAnswer);
tree = new DecisionTree<String>(question, no, yes);
} // end default constructor

public void play()
{

tree.reset();
while (!tree.isAnswer())
{

// ask current question
System.out.println(tree.getCurrentData());

if (Client.isUserResponseYes())
tree.advanceToYes();
else
tree.advanceToNo();
} // end while
assert tree.isAnswer(); // Assertion: leaf is reached

// make guess
System.out.println("My guess is " + tree.getCurrentData() +
". Am I right?");
if (Client.isUserResponseYes())
System.out.println("I win.");