– PROGRAMMING PART
1 Programming Assignment
A Java template containing an incomplete binary search tree implementation has been provided. Your assignment is to complete the insert() and remove() methods to implement the insertion and removal procedures of an AVL tree. The find() method is already implemented, and you are not permitted to change it or any other details of the AVLTree class besides the insert() and remove() methods. You may, however, add functions (or classes) as needed. You should read through the comments in the template carefully before starting, since you will need to use methods and data types the template provides, such as the TreeNode class which is used to contain each element of the tree.
1.1 Input Format
The main() function in the template contains testing code to perform a series of insert, find and remove operations based on test data entered by hand or read from a file. Input data consists of a set of strings to insert, one per line, followed by the token “###”, followed by a set of strings to search for in the tree. After searching for each element, the testing code in main() deletes the element if it is found in the tree. The following input file constructs a binary search tree containing the strings “Victoria”, “Vancouver”, “Saanich” and “Sidney”, then searches for the strings “Duncan”, “Nanaimo” and “Vancouver”: Victoria Vancouver Saanich Sidney ### Duncan Nanaimo Vancouver
1.2 Testing and Verification
Besides code to test the insert, find and remove methods, the template also contains functions to automatically verify the correctness of the constructed tree at each step. The testing code in main() will verify the binary search tree property and AVL property after each insertion and removal. These tests are time consuming (verifying the global tree properties is an O(n) operation), but can be helpful for debugging. The comments in the template explain how to enable each test. Do not use the tree verification functions directly in your code (let the code in main() handle everything for you). The tests will all be disabled automatically before marking (you do not have to disable them yourself before handing in your code).
2 Test Datasets
Three datasets are available on conneX. All three insert a list of place names (cities, towns, geographical features, etc.) into the tree. The place name data is based on the freely available geographical data repository at http://www.geonames.org. The ‘search’ section of each dataset contains 1865 strings, based on the names of streets around Victoria. Some of these values will be present in the tree (for example, ‘Waterloo’ is the name of a road in Victoria and a city in Ontario), but some searches will be unsuccessful. The table below gives the statistics for each dataset.
File Insertions Searches Total Present Not Present place_names_small.txt 22107 1865 362 1503 place_names_med.txt 43229 1865 527 1338 place_names_large.txt 122359 1865 757 1108
3 Sample Run The output of a model solution on the sample input data in Section 1.1 is given in the listing below. Console input is shown in blue. Since the number of inserted values is less than the value of the PrintTreeSizeThreshold constant in the template, the contents of the tree are printed out after the insertion phase. The contents are printed as an in-order traversal, with lower levels indented and the left child of each node visited first. For
example, in the output below, Vancouver is the root, Saanich is its left child and Sidney is the right child of Saanich
Enter a list of strings to store in the tree, one per line. To end the list, enter‘###’. Victoria Vancouver Saanich Sidney ### Read 4 strings. Enter a list of strings to search for in the tree, one per line. To end the list, enter‘###’. Duncan Nanaimo Vancouver ### Read 3 strings. Inserted 4 elements. Total Time (seconds): 0.00
Tree contents: ———- |– (no left child) |–Saanich | | | | |– (no left child) | |–Sidney | |– (no right child) | Vancouver | | |– (no left child) |–Victoria |– (no right child) ———- Tree contains 4 nodes and has height 2. Searched for 3 items (1 found and deleted, 2 not found). Total Time (seconds): 0.00
4 Evaluation Criteria The programming part of the homework will be marked using 100 working points (as usual, a max of 50 marks is reported on conneX for the programming part, and a max of 50 for the theory part of each homework). The insert and remove methods are each worth 50 working points, based on automated testing and human inspection. The implementation of the insert method will be marked using the following criteria:
Score (/50) Description 0 − 5 Submission does not compile or does not conform to the provided template. 5 − 25 The implemented algorithm correctly inserts nodes into the tree but does not perform AVL rebalancing. If the insertion algorithm does not preserve the binary search tree properties, no more than 25 working points will be given. 26 − 40 The implemented algorithm correctly inserts nodes into the tree and correctly performs AVL rebalanc- ing, but the insertion step does not have an O(log n) running time. 41 − 50 The implemented algorithm correctly inserts nodes and correctly performs AVL rebalancing, and has an O(log n) running time.
The implementation of the remove method will be marked using the following criteria: Score (/50) Description 0 − 5 Submission does not compile or does not conform to the provided template. 5 − 35 The implemented algorithm correctly removes nodes from the tree but does not perform AVL rebalancing. If the removal algorithm does not preserve the binary search tree properties, no more than 25 working points will be given. 36 − 45 The implemented algorithm correctly removes nodes from the tree and correctly performs AVL rebalanc- ing, but the does not have an O(log n) running time. 46 − 50 The implemented algorithm correctly removes nodes and correctly performs AVL rebalancing, and has an O(log n) running time. O(log n) running time.
To be properly tested, every submission must compile correctly as submitted, and must be based on the provided template. You may only submit one source file. If your submission does not compile for any reason (even trivial mistakes like typos), or was not based on the template, it will receive at most 10 out of 100 (5 out of 50 as reported on conneX). The best way to make sure your submission is correct is to download it from conneX after submitting and test it. You are not permitted to revise your submission after the deadline, and late submissions will not be accepted, so you should ensure that you have submitted the correct version of your code before the deadline. The conneX site will allow you to change your submission before the deadline if you notice a mistake. After submitting your assignment, conneX will automatically send you a confirmation email. If you do not receive such an email, your submission was not received. If you have problems with the submission process, send an email to the instructor well before the deadline. Unearned marks move to the final exam, but it is best to earn what you can along the way. Hand in what you can, and try to keep up with the course.