辅导 CS 300: Programming II – Fall 2024 P09 Leaderboard讲解 Java编程

CS 300: Programming II – Fall 2024

Due: 10:00 PM CT on MON 12/02

P09 Leaderboard

Overview

STUDENTS BE AWARE: WE ARE ENABLING PvP IN CS 300

Okay no we’re not. But if we were, this is how we’d keep track of who’s winning.

Hierarchical data structures allow us to efficiently maintain a sorted data structure, so our first attempt at this will be using a Binary Search Tree to maintain a leaderboard of the players of a game.

Grading Rubric

Learning Objectives

After completing this assignment, you should be able to:

● Describe the structure and functionality of a Binary Search Tree.

● Implement a Binary Search Tree with the relevant recursive algorithms for adding, removing, and traversing nodes.

● Demonstrate the utility of the Iterator, Iterable, and Comparable interfaces.

Additional Assignment Requirements and Notes

Keep in mind:

●    Pair programming is NOT ALLOWED for this assignment. You must complete and submit P09 individually.

● The ONLY external libraries you may use in your program are:

java.util.Iterator, java.util.NoSuch Element Exception

● Use of any other packages (outside of java.lang) is NOT permitted.

●   You are allowed to define any local variables you may need to implement the methods in this  specification (inside methods). You are NOT allowed to define any additional instance or static variables or constants beyond those specified in the write-up.

● You are allowed to define additional private helper methods.

●    Only Game and LeaderboardTester may contain a main method.

●   All classes and methods must have their own Javadoc-style method header comments in accordance with the CS 300 Course Style Guide .

●   Any source code provided in this specification may be included verbatim in your program without attribution.

●   All other sources must be cited explicitly in your program comments, in accordance with the Appropriate Academic Conduct guidelines.

●   Any use of ChatGPT or other large language models must be cited AND your submission MUST include screenshots of your interactions with the tool clearly showing all prompts and

responses in full. Failure to cite or include your logs is considered academic misconduct and will be handled accordingly.

● Run your program locally before you submit to Gradescope. If it doesn’t work on your computer, it will not work on Gradescope.

Need More Help?

Check out the resources available to CS 300 students here:

https://canvas.wisc.edu/courses/427315/pages/resources

CS 300 Assignment Requirements

You are responsible for following the requirements listed on both of these pages on all CS 300

assignments, whether you’ve read them recently or not. Take a moment to review them if it’s been a while:

● Appropriate Academic Conduct, which addresses such questions as:

○ How much can you talk to your classmates?

○ How much can you look up on the internet?

○ How do I cite my sources?

○ and more!

● Course Style. Guide, which addresses such questions as:

○ What should my source code look like?

○ How much should I comment?

○ and more!

Getting Started

1. Create a new project in Eclipse, called something like P09 Leaderboard.

a.    Ensure this project uses Java 17. Select “JavaSE-17” under “ Use an execution environment JRE” in the New Java Project dialog box.

b.    Do not create a project-specific package; use the default package.

2.    Download two (1) PROVIDED Java source files from the assignment page on Canvas . You will not

modify these files at all:

a. BSTNode.java

b. Game.java

3.    Download three (3) INCOMPLETE Java source files from the assignment page. You must complete these files:

a. Player.java – implements the Comparable interface

b. Leaderboard.java – implements the Iterable interface

c. LeaderboardTester.java

4.    Create one (1) new Java source file within that project’s src folder:

a. LeaderboardIterator.java – implements the Iterator interface

Implementation Requirements Overview

In this project you will implement an application that maintains a leaderboard of the players of a PvP (player-vs-player) game, ordered by their scores in that game. Players may challenge other players in the game, which may result in changes to the leaderboard.

We are NOT providing additional documentation beyond this writeup and the comments in the provided code.

Provided Classes

The following classes are provided in their entirety. You do not need to implement anything in them.

● BSTNode – a generic Binary Search Tree node.

● Game – a class which maintains a given game’s Leaderboard across PvP challenges.

Classes You Will Implement

You will completely or partially implement the following classes:

● Player – represents a single player of the game, including their name and numeric score. This class is nearly complete, but you must make these objects Comparable to other Players and complete the compareTo() method.

● Leaderboard – a binary search tree consisting of BSTNode. We have provided the public interface to this data structure, but the real work is done in the protected recursive helper methods, which you must implement.

● LeaderboardIterator – Leaderboard’s toString() method relies on an enhanced for loop, which in turn requires an iterator. This iterator must begin at the Player with the smallest score in the leaderboard, and iterate through the entirety of the leaderboard in increasing order.

● LeaderboardTester – a tester class for your BST implementation.

Organization of the Leaderboard

The core data structure in this project is the Leaderboard, which is a Binary Search Tree of Player objects. The BST orders the Players by their score (and breaks ties using the Players’ names), so the minimum value in the BST is the Player with the smallest score and the maximum value is the Player with the largest score.

We are providing you with a generic BSTNode class. Your Leaderboard must be built out of BSTNode (note Player, not T), and you will implement the relevant algorithms in the Leaderboard class. You will also need to implement Comparable for Player, which is the comparison method that you will use in Leaderboard.

Implementation Details and Suggestions

Begin by adding the required interfaces to your classes:

● Player must be Comparable (to what type?)

● Leaderboard must be Iterable (over what type?)

● LeaderboardIterator must be an Iterator (over what type?)

1. Implement compareTo() and Tests

Once Player is Comparable, you will need to complete the required compareTo() method according to the description in the comments. At this time you should also implement the first three tester methods  in LeaderboardTester:

● testCompareToDiffScore

● testCompareToSameScoreDiffName

● testCompareToEqual

The comments in the file are intended to provide some direction, but you are welcome to add additional tests as you see fit.

2. Implement Leaderboard and Tests

We recommend implementing the methods in the order below. Testing and debugging the latter methods will be significantly easier if you know the structure of your BST is correct, and implementing the earlier methods will help you get the structure correct. After implementing each of these methods, implement the relevant tester methods in LeaderboardTester, and test your implementation thoroughly! If you wait until the very end to test, you will have lots of weird and confusing bugs. See the next subsection for implementation/testing hints.

1. getMinScoreHelper and getMaxScoreHelper

2. countHelper

3. lookupHelper and the following test methods:

a.    testLookupRoot

b.   testLookupLeft

c.    testLookupRight

d.   testLookupNotPresent

4. addPlayerHelper and the following test methods:

a.    testAddPlayerEmpty

b.   testAddPlayer

c.    testAddPlayerDuplicate

5. nextHelper and the following test methods:

a.    testGetNextAfterRoot

b.   testGetNextAfterLeftSubtree

c.    testGetNextAfterRightSubtree

6. removeHelper and the remaining test methods

Note that you may NOT add ANY loops (of any kind) in the Leaderboard class. You MUST implement the above methods recursively. The loop present in the toString() method is the only permitted loop.

2.1 Some Hints

● Draw LOTS of pictures!

● Write tests as you go along. If you save testing for last you will be sad.

●   You MAY use the addPlayer() method to construct a tree for other testers, but for the lookup  tests in particular (since you won’t have completed that method yet) you will probably want to    check out the provided get Root() method in Leaderboard. You can add ONE player to the tree (we’ve provided the code for this), and then set up the rest of the tree by using the BSTNode methods set Left() and set Right().

○ Note that doing this will NOT affect the size field, so if you need to know how many nodes are present, you’ ll need to use count() instead.

●    For most of the Leaderboard tests, it is easiest if you use nearly identical Players that only differ by one aspect (e.g. all players are named “A” but have different scores, or all players have the default 1500 score but different names). This makes keeping track of the correct ordering easier.

● Remember: in every node, the left and right subtree should also be a valid binary tree. That is, if  you were to just yank out any left or right node anywhere in the tree (with its descendants), they could stand alone as a valid binary search tree.

●    If you are writing really long methods, you are probably overthinking it. My longest method by    far is removePlayerHelper, clocking in at about 40 lines with comments and whitespace, and it’s about twice as long as anything else in the class.

3. Implement the Iterator

The LeaderboardIterator implements the Iterator interface and iterates through all values in the tree in increasing order. This means that a full run of

for (Player p : leaderboard) System .out.println(p);

should begin with leaderboard.get MinScore() and end with leaderboard.get MaxScore(), and include leaderboard.size() number of different lines.

YOU MAY CHOOSE the implementation details of this class (constructor, data fields, etc) as long as it conforms to the following requirements:

1.    Implements the Iterator interface

2.    Constructed and initialized by Leaderboard’s iterator() method

3.    First call to next() returns leaderboard.get MinScore()

4.    Can call next() without an exception exactly leaderboard.size() number of times

5.    When hasNext() returns false, calling next() causes a NoSuchElementException Your Leaderboard class must also support use of an enhanced for loop as shown above.

4. [OPTIONAL] Run the Game

Now that your code is completed, you should be able to successfully run the Game.java code supported by your Leaderboard. Check out the sample output on the assignment page if you want to verify that everything is working as expected!

Assignment Submission

Hooray, you’ve finished this CS 300 programming assignment!

Once you’re satisfied with your work, both in terms of adherence to this specification and the academic conduct and style. guide requirements, make a final submission of your source code to Gradescope.

For full credit, please submit the following files (source code, not .class files):

● Player.java

● Leaderboard.java

● LeaderboardIterator.java

● LeaderboardTester.java

Additionally, if you used generative AI at any point during your development, you must include screenshots showing your FULL interaction with the tool(s).

Your score for this assignment will be based on the submission marked “active” prior to the deadline.

You may select which submission to mark active at any time, but by default this will be your most recent submission.