CS 1332 Homework 10: Graph Algorithms




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Graph Algorithms
For this assignment, you will be coding 4 different graph algorithms.
The first two algorithms are breadth-first search and depth-first search. These algorithms are search
algorithms that start at the given vertex and traverse the entire graph in a particular order (the order in
which the vertices are visited depend on whether you are doing breadth-first search or depth-first search,
the edges that are in the graph, and the order the adjacent vertices are listed). The order in which the
vertices are visited is then returned.
The next algorithm is Dijkstra’s algorithm. This algorithm finds the shortest path from one vertex
to all of the other vertices in the graph. You may assume that none of the edges will have a negative
The last algorithm is Kruskal’s minimum spanning tree algorithm. This algorithm finds the minimum
spanning tree of the graph and returns the edges that make up that minimum spanning tree.
For all algorithms, you may assume that you are allowed to go from a vertex to itself, and that the
distance of that is 0. In addition, the graph with be either directed or undirected; it will not be a mix
of the two.
A word of advice: look over and understand the framework before starting the homework. Understanding how the graphs are represented and how the relevant data structures work will be instrumental
to this homework.
A note on JUnits
We have provided a very basic set of tests for your code, in GraphAlgorithmsStudentTests.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
Homework 10: Graph Algorithms Due: See T-Square
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.
Visualizations of Graphs
The directed graph used in the student tests is:
2 3
The undirected graph used in the student tests is:
4 3
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 off a point for every style error that
occurs. If you feel like what you wrote is in accordance with good style but still sets off the style checker
please email Carey MacDonald (careyjmac@gatech.edu) with the subject header of “CheckStyle XML”.
Javadoc any helper methods you create in a style similar to the existing Javadocs. Like the existing
Javadocs, the Javadocs for your helper method(s) must describe well what the method does, what
each parameter means (if any), and what the returned value is (if any). If a method is overridden or
implemented from a superclass or an interface, you may use @Override instead of writing Javadocs.
When throwing exceptions, you must include a message by passing in a String as a parameter. The message 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:
Homework 10: Graph Algorithms Due: See T-Square
throw new PDFReadException(“Did not read PDF, will lose points.”);
throw new IllegalArgumentException(“Cannot insert null data into data structure.”);
If available, use the generic type of the class; do not use the raw type of the class. For example, use new
LinkedList() instead of new LinkedList(). Using the raw type of the class will result in a
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
• Objects class
• Stack class
• Collections class
• Collection.toArray()
• Reflection APIs
• Inner, nested, or anonymous classes
Debug print statements are fine, 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
off points.
The following file(s) have been provided to you. There are several, but you will edit only one of them.
1. GraphAlgorithms.java
This is the class in which you will implement the different graph algorithms. Feel free to add private
static helper methods but do not add any new public methods, new classes, instance
variables, or static variables.
Homework 10: Graph Algorithms Due: See T-Square
2. GraphAlgorithmsStudentTests.java
This is the test class that contains a set of tests covering the basic operations on the GraphAlgorithms
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.
3. Graph.java
This class represents a graph. Do not modify this file.
4. Vertex.java
This class represents a vertex in the graph. It contains the data in this vertex. Do not modify
this file.
5. Edge.java
This class represents an edge in the graph. It contains the vertices connected to this edge, its
weight, and whether or not it is directed. Do not modify this file.
6. VertexDistancePair.java
This class holds together a vertex and a distance. It is meant to be used with Dijkstra’s algorithm.
Do not modify this file.
7. DisjointSet.java
This class implements the disjoint-set data structure. It is meant to be used with Kruskal’s algorithm. Do not modify this file.
You must submit all of the following file(s). Please make sure the filename matches the filename(s)
below, and that only the following file(s) are present. T-Square does not delete files from old uploads;
you must do this manually. Failure to do so may result in a penalty.
After submitting, be sure you receive the confirmation email from T-Square, and then download your
uploaded files 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.
1. GraphAlgorithms.java