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
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 inorder
traversal, with lower levels indented and the left child of each node visited first. For3
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:4
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 rebalancing, 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 rebalancing, 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
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