CS1332 Assignment 2-Binary Search Tree Solution

Binary Search Tree
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 the left and right child nodes. The BST must follow the order property: for any given node, its left child and all of its children must be less than the current node while its right child and all of its children 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: the 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.
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. These wrapper methods will just call another private helper method that is recursive. 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
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. A leaf node has a height of 0. Based on this recursive definition, this means that null nodes have a height of -1.
Comparable
As stated, the data in the BST must implement the Comparable interface. As you’ll see in the files, the generic typing has been specified 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
• If positive, then data1 > data2.
• If negative, then data1 < data2.
• 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.
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
JUnits
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.
Style and Formatting
Javadocs
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 HAPPENED”, 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.’’);
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
• package
• System.arraycopy()
• clone()
• assert()
• Arrays class
• Array class
• 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.
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). Please make sure the filename(s) matches the filename(s) below, and that only the following file(s) are present. The only exception is that Canvas will automatically append a -n depending on the submission number to the file name. This is expected and will be handled by the TAs when grading as long as the file name before this add-on matches what is shown below. If you resubmit, be sure only one copy of the 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.
Once submitted, double check that it has uploaded properly on Canvas. To do this, download your uploaded files to a new folder, copy over the support files, recompile, and run. It is your sole responsibility to re-test your submission and discover editing oddities, upload issues, etc.
1. BST.java