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CSCI 1933 Project 3
Herding the Elephants 2.0: Linked Lists
Note: The project is due on Friday, March 23rd by 11:55 PM.
Instructions
Please read and understand these expectations thoroughly. Failure to follow these instructions
could negatively impact your grade. Rules detailed in the course syllabus also apply but will not
necessarily be repeated here.
• Due: The project is due on Friday, March 23rd, 2018 by 11:55 PM.
• Identification: Place you and your partner’s x500 in a comment in all files you submit. For
example, //Written by shino012 and hoang159.
• Submission: Submit a zip or tar archive on Moodle containing all your java files. You are
allowed to change or modify your submission, so submit early and often, and verify that all
your files are in the submission.
Failure to submit the correct files will result in a score of zero for all missing parts. Late
submissions and submissions in an abnormal format (such as .rar or .java) will be penalized.
Only submissions made via Moodle are acceptable.
• Partners: You may work alone or with one partner. Failure to tell us who is your
partner is indistinguishable from cheating and you will both receive a zero. Ensure
all code shared with your partner is private.
• Code: You must use the exact class and method signatures we ask for. This is because we use
a program to evaluate your code. Code that doesn’t compile will receive a significant penalty.
Code should be compatible with Java 8, which is installed on the CSE Labs computers.
• Questions: Questions related to the project can be discussed on Moodle in abstract. This
relates to programming in Java, understanding the writeup, and topics covered in lecture and
labs. Do not post any code or solutions on the forum. Do not e-mail the TAs your
questions when they can be asked on Moodle.
• Grading: Grading will be done by the TAs, so please address grading problems to them
privately.
IMPORTANT: You are NOT permitted to use ANY built-in libraries, classes, etc.
Double check that you have NO import statements in your code, except for those
explicitly permitted.
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CSCI 1933 PROJECT 3
Due: Friday, March 23th, 2018
Code Style
Part of your grade will be decided based on the “code style” demonstrated by your programming.
In general, all projects will involve a style component. This should not be intimidating, but it is
fundamentally important. The following items represent “good” coding style:
• Use effective comments to document what important variables, functions, and sections of
the code are for. In general, the TA should be able to understand your logic through the
comments left in the code.
Try to leave comments as you program, rather than adding them all in at the end. Comments
should not feel like arbitrary busy work - they should be written assuming the reader is fluent
in Java, yet has no idea how your program works or why you chose certain solutions.
• Use effective and standard indentation.
• Use descriptive names for variables. Use standard Java style for your names: ClassName,
functionName, variableName for structures in your code, and ClassName.java for the file
names.
Try to avoid the following stylistic problems:
• Missing or highly redundant, useless comments. int a = 5; //Set a to be 5 is not helpful.
• Disorganized and messy files. Poor indentation of braces ({ and }).
• Incoherent variable names. Names such as m and numberOfIndicesToCount are not useful. The former is too short to be descriptive, while the latter is much too descriptive and
redundant.
• Slow functions. While some algorithms are more efficient than others, functions that are
aggressively inefficient could be penalized even if they are otherwise correct. In general,
functions ought to terminate in under 5 seconds for any reasonable input.
The programming exercises detailed in the following pages will both be evaluated for code style.
This will not be strict – for example, one bad indent or one subjective variable name are hardly a
problem. However, if your code seems careless or confusing, or if no significant effort was made to
document the code, then points will be deducted.
In further projects we will continue to expect a reasonable attempt at documentation and style as
detailed in this section. If you are confused about the style guide, please talk with a TA.
2
CSCI 1933 PROJECT 3
1
Due: Friday, March 23th, 2018
Introduction
IMPORTANT: This project utilizes similar concepts and java skills to Project 2. For brevity,
this write-up omits discussions of generics and interfaces. For more information, see the
instructions for Project 2.
In this project you are going to implement a list [1] interface to construct your own LinkedList
data structure. Using this you will construct an ElephantHerd to hold a family of elephants [2].
1.1
LinkedList Implementation
The first part of this project will be to implement a linked list. Create a class LinkedList that
implements all the methods in List interface. Recall that to implement the List interface and use
the generic compatibility with your code, LinkedList should have following structure:
public class LinkedList> implements List {
...
}
The underlying structure of a linked list is a node. This means you will have an instance variable
that is the first node of the list. The provided Node.java contains a generic node class that you
will use for your linked list implementation∗ .
Your LinkedList class should have a single constructor:
public LinkedList() {
...
}
that initializes the list to an empty list.
Implementation Details
• In addition to the methods described in the List interface, the LinkedList class should
contain a private class variable isSorted. This should be initialized to true in the constructor
(because it is sorted if it has no elements) and updated when the list is sorted, or more elements
∗
You may implement your linked list as a headed list, i.e., the first node in the list is a ‘dummy’ node and the
second node is the first element of the list, or a non-headed list, i.e., the first node is the first element of the list.
Depending on how you choose to implement your list, there will be some small nuances.
3
CSCI 1933 PROJECT 3
Due: Friday, March 23th, 2018
are added or set. For the purposes of this class, isSorted is only true if the list is sorted in
ascending order.
• Initially and after a call to clear(), the size should be zero and your list should be empty.
• In sort(), do not use an array or ArrayList to sort the elements. You are required to
sort the values using only the linked list data structure. You can move nodes or swap values
but you cannot use an array to store values while sorting.
• Depending on your implementation, remember that after sorting, the former first node may
not be the current first node.
After you have implemented your LinkedList class, include junit tests that test all functionality.
2
An Elephant Herd
Slightly modify your class ElephantHerd from Project 2 to use an underlying LinkedList rather
than an ArrayList. Then verify that the methods still work as intended.
If you did the previous project correctly, this step should only require the modification of one line
of code.
3
Analysis
Now that you have implemented and used both an array list and linked list, which one is better?
Which methods in List are more efficient for each implementation?
For each of the 13 methods in List, compare the runtime (Big-O) for each method and implementation. Ignore any increased efficiency caused by the flag isSorted. Include an analysis.txt
or analysis.pdf with your submission structured as follows:
Method
boolean add(T element)
boolean add(int index, T element)
..
.
ArrayList Runtime
O(...)
O(...)
..
.
LinkedList Runtime
O(...)
O(...)
..
.
Explanation
...
...
..
.
Your explanation for each method only needs to be a couple sentences briefly justifying your
runtimes.
4
CSCI 1933 PROJECT 3
4
Due: Friday, March 23th, 2018
Iterators (Honors)
Note: This section is **required** for students in Honors section only. Optional for others but no
extra credit.
Much like in Project 2, you will create an iterator for the LinkedList class.
This section will require you to write another class, and to make modifications to the LinkedList
class.
You will write a LinkedListIterator class which will iterate over a list. This iterator should
implement java’s iterator interface in addition to the List interface. Make sure to import
java.util.Iterator. This class will have two functions and a constructor. It will also need class
variables to store a pointer to its LinkedList and the current index.
1. LinkedListIterator(LinkedList a) – the constructor. This constructor will never be directly called by the user. Instead, it will be called in the iterator() function in the LinkedList
class.
2. hasNext() – This will return true if there is another object to iterate on, and false otherwise.
3. next() – This will return the next object if there is one, and null otherwise.
The first line of the LinkedListIterator class should be as follows:
private class LinkedListIterator> implements Iterator
Note that in order for a class to be private, it must be in the same document as another class,
and within the curly braces of that class. This means that LinkedListIterator should be in
the LinkedList.java file, and should be in the curly braces of LinkedList, with the methods of
LinkedList.
You will also need to make some modification to the LinkedList class. First, the class now needs
to implement Iterable.
public class LinkedList> implements Iterable, List
Secondly, you will need to add the method public Iterator iterator(). This method should
return a LinkedListIterator object by calling the LinkedListIterator constructor and passing
itself to the constructor (via the this keyword).
Make sure to create junit tests to ensure that your iterator functions as desired.
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