Description
Important
There are general homework guidelines you must always follow. If you fail to follow any of the following guidelines, you risk receiving a 0 for the entire assignment.
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All submitted code must compile under JDK 8. This includes unused code, so don’t submit extra les that don’t compile. Any compile errors will result in a 0.
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Do not include any package declarations in your classes.
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Do not change any existing class headers, constructors, instance/global variables, or method sig-natures. For example, do not add throws to the method headers since they are not necessary.
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Do not add additional public methods.
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Do not use anything that would trivialize the assignment. (e.g. Don’t import/use java.util.ArrayList for an ArrayList assignment. Ask if you are unsure.)
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Always be very conscious of e ciency. Even if your method is to be O(n), traversing the structure multiple times is considered ine cient unless that is absolutely required (and that case is extremely rare).
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You must submit your source code, the .java les, not the compiled .class les.
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Only the last submission will be graded. Make sure your last submission has all required les. Resubmitting will void all previous submissions.
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After you submit your les, redownload them and run them to make sure they are what you intended to submit. You are responsible if you submit the wrong les.
Collaboration Policy
Every student is expected to read, understand and abide by the Georgia Tech Academic Honor Code.
When working on homework assignments, you may not directly copy code from any source (other than your own past submissions). You are welcome to collaborate with peers and consult external re-sources, but you must personally write all of the code you submit. You must list, at the top of each le in your submission, every student with whom you collaborated and every resource you consulted while completing the assignment.
You may not directly share any les containing assignment code with other students or post your code publicly online. If you wish to store your code online in a personal private repository, you can use Github Enterprise to do this for free.
The only code you may share is JUnit test code on a pinned post on the o cial course Piazza. Use JUnits from other students at your own risk; we do not endorse them. See each assignment’s PDF for more details. If you share JUnits, they must be shared on the site speci ed in the Piazza post, and not anywhere else (including a personal GitHub account).
Violators of the collaboration policy for this course will be turned into the O ce of Student Integrity.
Style and Formatting
It is important that your code is not only functional, but written clearly and with good programming style. Your code will be checked against a style checker. The style checker is provided to you, and is
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Homework 3: BST Due: See Canvas
located on Canvas. It can be found under Files, along with instructions on how to use it. A point is deducted for every style error that occurs. If there is a discrepancy between what you wrote in accordance with good style and the style checker, then address your concerns with the Head TA.
Javadocs
Write javadocs for any helper methods you create in a style similar to the existing javadocs. Any javadocs you write must be useful and describe the contract, parameters, and return value of the method. Random or useless javadocs added only to appease checkstyle will lose points.
Vulgar/Obscene Language
Any submission that contains profanity, vulgar, or obscene language will receive an automatic zero on the assignment. This policy applies not only to comments/javadocs, but also things like variable names.
Exceptions
When throwing exceptions, you must include a message by passing in a String as a parameter. The message must be useful and tell the user what went wrong. \Error”, \BAD THING HAP-PENED”, and \fail” are not good messages. The name of the exception itself is not a good message. For example:
Bad: throw new IndexOutOfBoundsException(‘‘Index is out of bounds.’’);
Good: throw new IllegalArgumentException(‘‘Cannot insert null data into data structure.’’); In addition, you may not use try catch blocks to catch an exception unless you catching an exception you have explicitly thrown yourself with the throw new ExceptionName(‘‘Exception Message’’); syn-
tax (replacing ExceptionName and Exception Message with the actual exception name and message respectively).
Generics
If available, use the generic type of the class; do not use the raw type of the class. For example, use new LinkedList<Integer>() instead of new LinkedList(). Using the raw type of the class will result in a penalty.
Forbidden Statements
You may not use these in your code at any time in CS 1332.
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package
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System.arraycopy()
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clone()
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assert()
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Arrays class
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Array class
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Thread class
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Collections class
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Collection.toArray()
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Re ection APIs
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Homework 3: BST Due: See Canvas
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Inner or nested classes
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Lambda Expressions
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Method References (using the :: operator to obtain a reference to a method)
If you’re not sure on whether you can use something, and it’s not mentioned here or anywhere else in the homework les, just ask.
Debug print statements are ne, but nothing should be printed when we run your code. We expect clean runs – printing to the console when we’re grading will result in a penalty. If you submit these, we will take o points.
JUnits
We have provided a very basic set of tests for your code. These tests do not guarantee the correctness of your code (by any measure), nor do they guarantee you any grade. You may additionally post your own set of tests for others to use on the Georgia Tech GitHub as a gist. Do NOT post your tests on the public GitHub. There will be a link to the Georgia Tech GitHub as well as a list of JUnits other students have posted on the class Piazza.
If you need help on running JUnits, there is a guide, available on Canvas under Files, to help you run JUnits on the command line or in IntelliJ.
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You are to code a binary search tree, BST, which is a collection of nodes, each having a data item and references pointing to left and right child nodes. The BST must follow the order property: for any given node, its left child’s data and all of its children’s data must be less than the current node while its right child’s data and all of its children’s data must be greater than the current node. In order to compare the data, all elements added to the tree must implement Java’s generic Comparable interface.
It will have two constructors: a no-argument constructor (which should initialize an empty tree), and a constructor that takes in a collection of data to be added to the tree, and initializes the tree with this collection of data.
You may import Java’s LinkedList/ArrayList classes for the 4 traversal methods and findPathBetween, but only for these methods.
Recursion
Since trees are naturally recursive structures, all methods that are not O(1) must be implemented recursively, except for level order traversal. You’ll also notice that a lot of the public method stubs we’ve provided do not contain the parameters necessary for recursion to work, so these public methods act as \wrapper methods” for the user to use. You will have to write private recursive helper methods and call them in these wrapper methods. Don’t forget to write javadocs for all private helper methods written. To reiterate, do not change the method headers for the provided methods.
For methods that change the structure of the tree in some way, we highly recommend you use a technique taught in class called pointer reinforcement. It is not required, but it will make the homework cleaner, and it’ll also help greatly when we get to a later homework.
Nodes
The binary search tree consists of nodes. A class BSTNode is provided to you. BSTNode has getter and setter methods to access and mutate the structure of the nodes.
Methods
You will implement all standard methods for a Java data structure (add, remove, etc.) in addition to a few other methods (such as traversals). You must follow the requirements stated in the javadocs of each method you implement.
Traversals
You will implement 4 di erent ways of traversing a tree: pre-order traversal, in-order traversal, post-order traversal, and level-order traversal. The rst 3 MUST be implemented recursively; level-order is best implemented iteratively. For a level-order traversal, you may use Java’s Queue interface (and an implementing class for it such as LinkedList).
Height
You will implement a method to calculate the height of the tree. The height of any given node is max(left node’s height, right node’s height) + 1. When doing this calculation, a null node has a height of -1. As such, a leaf node will have a height of 0, which is calculated by max(-1, -1) + 1.
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Homework 3: BST Due: See Canvas
Comparable
As stated, the data in the BST must implement the Comparable interface. As you’ll see in the les, the generic typing has been speci ed to require that it implements the Comparable interface. You use the interface by making a method call like data1.compareTo(data2). This will return an int, and the value tells you how data1 and data2 are in relation to each other
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If positive, then data1 is larger than data2.
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If negative, then data1 is smaller than data2.
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If zero, then data1 equals data2.
Note that the returned value can be any integer in Java’s int range, not just -1, 0, 1.
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Homework 3: BST Due: See Canvas
Grading
Here is the grading breakdown for the assignment. There are various deductions not listed that are incurred when breaking the rules listed in this PDF and in other various circumstances.
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Methods: |
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constructor |
4pts |
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add |
14pts |
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remove |
20pts |
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get |
5pts |
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contains |
5pts |
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preorder |
3pts |
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inorder |
3pts |
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postorder |
3pts |
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levelorder |
3pts |
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height |
3pts |
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clear |
2pts |
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ndPathBetween |
10pts |
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Other: |
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Checkstyle |
10pts |
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E ciency |
15pts |
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Total: |
100pts |
Provided
The following le(s) have been provided to you. There are several, but we’ve noted the ones to edit.
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BST.java
This is the class in which you will implement the BST. Feel free to add private helper methods but do not add any new public methods, inner/nested classes, instance variables, or static variables.
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BSTNode.java
This class represents a single node in the tree. It encapsulates the data, and the left and right references. Do not alter this le.
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BSTStudentTest.java
This is the test class that contains a set of tests covering the basic operations on the BST class. It is not intended to be exhaustive and does not guarantee any type of grade. Write your own tests to ensure you cover all edge cases.
Deliverables
You must submit all of the following le(s) to the course Gradescope. Make sure all le(s) listed below are in each submission, as only the last submission will be graded. Make sure the lename(s) matches the lename(s) below, and that only the following le(s) are present. Do NOT submit BSTNode.java for this homework; if you do, your homework will not compile on Gradescope. If you resubmit, be sure only one copy of each le is present in the submission. If there are multiple les, do not zip up the les before submitting; submit them all as separate les.
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Homework 3: BST Due: See Canvas
Once submitted, double check that it has uploaded properly on Gradescope. To do this, download your uploaded le(s) to a new folder, copy over the support le(s), recompile, and run. It is your sole responsibility to re-test your submission and discover editing oddities, upload issues, etc.
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BST.java
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