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Homework 5: AVL Trees Solution

AVL




You are required to implement an AVL tree. An AVL is a special type of binary search tree that follows all the same rules: each node has 0-2 children, all data in the left subtree is less than the node’s data, and all data in the right subtree is greater than the node’s data. The AVL di ers from the BST with its own self-balancing rotations, which you must implement.




All methods in the AVL tree that are not O(1) must be implemented recursively, except for level-order traversal. Good recursion with simple, focused states is strongly encouraged for this assignment in particular.




Your AVL tree will implement the AVL interface provided. It will have two constructors: a no-argument constructor (which should initialize an empty tree), and a constructor that takes in data to be added to the tree, and initializes the tree with this data.




Balancing




Each node has two additional instance variables, height and balanceFactor. The height variable represents the height of the node (recall that a node’s height is max(child nodes’ heights)+1. The balance factor of a node is equal to its left child’s height minus its right child’s height. The tree should rotate appropriately to make sure it’s always balanced.




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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Homework 5: AVL Trees
Due: See T-Square








Methods:














add
15pts












remove
15pts












get
7pts












contains
7pts












traversals
12pts












threshold
7pts












height
3pts












clear
4pts












constructor
5pts












Other:














Checkstyle
10pts












E ciency
15pts












Total:
100pts















Keep in mind that add functions are necessary to test other functions, so if an add doesn’t work, remove tests might fail as the items to be removed were not added correctly. Additionally, the size function is used many times throughout the tests, so if the size isn’t updated correctly or the method itself doesn’t work, many tests can fail.




A note on JUnits




We have provided a very basic set of tests for your code, in AVLStudentTests.java. These tests do not guarantee the correctness of your code (by any measure), nor does it 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 T-Square under Resources, to help you run JUnits on the command line or in IntelliJ.




Style and Formatting




It is important that your code is not only functional but is also written clearly and with good style. We will be checking your code against a style checker that we are providing. It is located in T-Square, under Resources, along with instructions on how to use it. We will take o a point for every style error that occurs. If you feel like what you wrote is in accordance with good style but still sets o the style checker please email Grayson Bianco (gbianco6@gatech.edu) with the subject header of \CheckStyle XML".




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.




Exceptions




When throwing exceptions, you must include a message by passing in a String as a parameter. The mes-sage 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:




throw new PDFReadException("Did not read PDF, will lose points.");










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Homework 5: AVL Trees Due: See T-Square










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




You may not use these in your code at any time in CS 1332.




break may only be used in switch-case statements




continue package




System.arraycopy() clone()




assert()




Arrays class Array class




Collections class




Collection.toArray()




Re ection APIs




Inner, nested, or private classes







Debug print statements are ne, but nothing should be printed when we run them. We expect clean runs - printing to the console when we’re grading will result in a penalty. If you use these, we will take o points.




Provided




The following le(s) have been provided to you. There are several, but you will only edit one of them.




AVLInterface.java



This is the interface you will implement in AVL. All instructions for what the methods should do are in the javadocs. Do not alter this le.




AVL.java



This is the class in which you will implement AVLInterface. Feel free to add private helper methods but do not add any new public methods, inner/nested classes, instance variables, or static variables.




AVLNode.java



This class represents a single node in the AVL tree. Do not alter this le.







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Homework 5: AVL Trees Due: See T-Square










AVLStudentTests.java



This is the test class that contains a set of tests covering the basic operations on the AVL 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). Please make sure the lename matches the lename(s) below, and that only the following le(s) are present. T-Square does not delete les from old uploads; you must do this manually. Failure to do so may result in a penalty.




After submitting, be sure you receive the con rmation email from T-Square, and then download your uploaded les to a new folder, copy over the interfaces, recompile, and run. It is your responsibility to re-test your submission and discover editing oddities, upload issues, etc.




AVL.java







































































































































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