CS 445: Data Structures
Fall 2018
Assignment 1
Assigned: Thursday, September 13 Due: Thursday, September 27 11:59 PM
1 Motivation
In CS 445, we often discuss the importance of data structure design and implementation
to the wide variety of computing applications. Despite decades of study and development
of common libraries, organizations must still regularly develop custom data structures to
fulfill their applications’ specific needs, and as such the field remains hugely relevant to both
computer scientists and software engineers.
In this assignment, you will implement two data structures to satisfy their specifications,
which are provided in the form of interfaces.
Note: Your goal in this assignment is to write classes that faithfully implement
the ADTs described in the interfaces. Sample client code is provided as one example
of how the classes may be used. However, this sample code does not test all of the
capabilities you are asked to implement, and thus your goal is not simply to make this
sample code work. You are strongly encouraged to write your own test client as well, to
further test that all operations of your classes work in all the corner cases described in
the interfaces.
2 Provided code
First, look over the provided code. You can find this code on Pitt Box in a folder named
cs445-a1-abc123, where abc123 is your Pitt username.
The SetInterface<E> interface describes a set, a data structure similar in concept to a bag
except that it does not allow duplicates. It is a generic interface that declares abstract
methods for adding an item, removing an item (specified or unspecified), checking if the set
is empty, determining the number of items in the set, and fetching the items from the set
into an array. You should not modify this interface.
The SetFullException class is included to allow potential implementations of SetInterface that
have a fixed capacity. Your implementation should not be fixed capacity, and thus should
not throw this exception.
The GroceryItem class is a simple way of representing a grocery item and its quantity.
This class contains two constructors, a getter and setter for the quantity, a getter for the
1
description, and some utility methods (for checking equality and converting to string for
printing). Note that two GroceryItem objects are considered “equal” if they have the same
description, even if their quantity is different! You should not modify this class.
The GroceriesInterface interface describes a collection of GroceryItem objects. Its intention is
to be used similarly to a shopping list, although it is not a truly a list; it is to be backed by
the Set class, so it is unordered and does not permit duplicates. It declares abstract methods
for adding and removing (i.e., increasing or decreasing quantity for) GroceryItem objects in the
collection. It also has a method for overwriting the quantity on a GroceryItem, as opposed
to strictly increasing or decreasing it. Finally, it has a method to print all items in the
collection.
The GroceriesExample class (not in the cs445.a1 package) shows one example usage of the
Groceries data structure. It demonstrates a few features, but is not a thorough test.
3 Tasks
3.1 Implement Set, 65 points
Develop the generic class, Set<E>, a dynamic-capacity array-based implementation of the
Set ADT described in SetInterface<E>. Include this class in package cs445.a1. Read the comments
in the interface (and this document!) carefully to ensure you implement it properly; it will
be graded using a client that assumes all of the functionality described in the SetInterface,
not just the behavior you need to implement GroceriesInterface!
You must include a constructor public Set(int capacity) that initializes the array to the
specified initial capacity, and a constructor public Set() that uses a reasonable default initial
capacity. Finally, you should provide a constructor public Set(E[] entries) that initializes the
set to include each of the provided entries. Note that this constructor must still create
its own backing array, and not adopt the argument as a data member; it must also skip
all duplicates and null values in the provided array, to satisfy the data structure’s usual
assumptions. Whenever the capacity is reached, the array must resize, using the techniques
discussed in lecture (i.e., you should never throw SetFullException).
Method Points
Set() 4
Set(int) 4
Set(E[]) 9
int getSize() 4
boolean isEmpty() 4
boolean add(E) 7
E remove(E) 7
E remove() 6
void clear() 5
boolean contains(E) 6
Object[] toArray() 9
2
3.2 Implement Groceries, 35 points
Develop the Groceries class, an implementation of the ADT described in GroceriesInterface.
Include this class in package cs445.a1. Read the interface carefully (including comments) to
ensure you implement it properly. As with Set, it will be graded using a client that expects
the full functionality described in its interface. The Groceries class can be seen as a client of
the Set data structure. Use composition with your Set<E> class to store the items as a data
member of type Set<GroceryItem>. Include a constructor public Groceries() that initializes the set.
Method Points
Groceries() 3
void addItem(GroceryItem) 7
void removeItem(GroceryItem) 7
int modifyQuantity(GroceryItem) 9
void printAll() 9
3.3 Testing
GroceriesExample is provided as an example client of the Groceries class. It does not exhaustively
test the functionality of both classes you must write. You are responsible for ensuring your
implementations work properly in all cases, even those not tested by GroceriesExample, and
follow the ADTs described in the provided interfaces. Thus, it is highly recommended that
you write additional test client code to test all of the corner cases described in the interfaces.
For help getting started, re-read the section of the textbook starting at Chapter 2.16.
Note: For functionality that cannot be tested (e.g., methods that crash, cannot be
compiled), up to 1/2 points will be awarded by inspection. At this level, turning in
code that crashes or does not compile is not acceptable and will not yield success.
4 Submission
Upload your java files in the provided Box directory. If you accidentally overwrite the
provided interfaces or GroceryItem class, remember to restore them to their original versions.
You may not make changes to the functionality in these files.
All programs will be tested on the command line, so if you use an IDE to develop your
program, you must export the java files from the IDE and ensure that they compile and run
on the command line. Do not submit the IDE’s project files. Your TA should be able to
download your cs445-a1-abc123 directory from Box, and compile and run your code as discussed
in Lab 1. For instance, javac cs445/a1/Groceries.java should compile your Groceries class. In
addition, javac GroceriesExample.java and java GroceriesExample must compile and run GroceriesExample.
In addition to your code, you may wish to include a README.txt file that describes features
of your program that are not working as expected, to assist the TA in grading the portions
that do work as expected.
http://www.6daixie.com/contents/9/1823.html
Your project is due at 11:59 PM on Thursday, September 27. You should upload your
progress frequently, even far in advance of this deadline: No late submissions will be
accepted.
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