SOLVED:Homework 4: BST

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 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

Javadoc any helper methods you create in a style similar to the existing javadocs. If a method is overridden or implemented from a superclass or an interface, you may use @Override instead of writing 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 are catching an exception you have explicitly thrown yourself with the throw new ExceptionName(‘‘Exception Message’’); syntax (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.

    • package

    • System.arraycopy()

    • clone()

    • assert()

    • Arrays class

    • Array class


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Homework 4: BST    Due: See Canvas



    • Thread class

    • Collections class

    • Collection.toArray()

    • Reflection APIs

    • Inner or nested classes

    • Lambda Expressions

    • 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 files, just ask.

Debug print statements are fine, 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 off 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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Homework 4: BST



Binary Search Tree

Due: See Canvas

You are to code a binary search tree, BST, which is a collection of nodes, each having a data item and a reference pointing to a left and a 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, but only use them in 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. All of these helper methods must be private. 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 different ways of traversing a tree: pre-order traversal, in-order traversal, post-order traversal, and level-order traversal. The first 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 the tree is defined as the height of its root. The height of any given node is max(left node’s height, right node’s height)

    • 1. When doing this calculation, a leaf node has a height of 0 and a null node has a height of -1.






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Homework 4: BST    Due: See Canvas



Comparable

As stated, the data in the BST must implement the Comparable interface. As you’ll see in the files, the generic typing of the BST and BSTNode classes will enforce this Comparable data requirement. 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

    • If the int is positive, then data1 is larger than data2.

    • If the int is negative, then data1 is smaller than data2.

    • If the int is 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 4: 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.

Methods:



constructor
4pts


add
14pts


remove
20pts


get
5pts


contains
5pts


preorder
3pts


inorder
3pts


postorder
3pts


levelorder
3pts


height
3pts


clear
2pts


findPathBetween
10pts


Other:



Checkstyle
10pts


Efficiency
15pts


Total:
100pts



Provided

The following file(s) have been provided to you. There are several, but we’ve noted the ones to edit.

    1. 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.

    2. 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 file.

    3. 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 file(s) to the course Gradescope. Make sure all file(s) listed below are in each submission, as only the last submission will be graded. Make sure the filename(s) matches the filename(s) below, and thatonly the following file(s) are present. DoNOT 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 file is present in the submission. If there are multiple files, do not zip up the files before submitting; submit them all as separate files.



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Homework 4: BST    Due: See Canvas



Once submitted, double check that it has uploaded properly on Gradescope. To do this, download your uploaded file(s) to a new folder, copy over the support file(s), recompile, and run. It is your sole responsibility to re-test your submission and discover editing oddities, upload issues, etc.

    1. BST.java




























































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