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# CS1027: Assignment 3

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CS1027: Assignment 3

Mazes can be solved by computers using a variety of algorithms. This time we will use some Artificial
Intelligence (AI) to solve the maze more efficiently! This assignment uses many of the same concepts
and files as assignment 2.
This picture shows a completed maze (maze2.txt) using this algorithm.
The end of the maze was found.
38 steps to the end.
There are still 4 Hexagons in the
queue.
109 steps were taken.
Functional Specifics
For this assignment you are given a number of classes to use, and you will also use some of the classes
from Lecture. You will create classes: MazeSolverToo, PriorityNode (basically a node class
with a priority attribute), and LinkedPriorityQueue (I recommend copying the normal queue
class and then adding a special enqueue based on priority). You are provided with the
The classes you will mostly be interacting with are Maze, Hexagon, and the classes you make.
The API for the provided classes will orient you to their methods: API Reference. In other words,
before you start, familiarize yourself with the classes, specifically the altered Hexagon class!!! Be sure
to read the description of the class near the top of the page and the available methods provided by the
class.
There are a few differences from assignment 2 to note here. There is a different set of Hexagon Types,
Hexagons also have a stepsToMe attribute, and there are a few important new methods you should
investigate.
The tiles will display in different colours so you can track your MazeSolverToo’s progress.
You’re going to actually use some AI to intelligently find the end of the maze! You will use something
called A* . Basically, it’s f(x) = g(x) + h(x), where x is a Hexagon, f(x) is a priority of x, g(x) is how
far x is from the start (look at stepsToMe), and h(x) is some heuristic – how far we think x is from the
end (you should look into distanceToEnd()).
So instead of using a stack, you will be using a queue. Actually, you will be using a priority queue
where the priority will be f(x). If you want to know what a priority queue is, then I suggest you start
Googling!
High Level Algorithm:
 Try to create a maze object reference
 Create a Hexagon reference and get the start Hexagon tile from the maze and add it to the
priority queue
 while queue is not empty
o dequeue
o Is this the end?
o Check node’s neighbours and add them to priority queue based on f(x)
o Note: Each time through we need to update the maze window with a call to repaint()
 Once we have searched the maze using the above algorithm, print out the following using a
System.out.println or .format:
o If the end was found, or if it was not found
o The number of steps to get to finish
o How many tiles were still in the priority queue
o Number of steps taken
Code similarities are both violations of Academic Dishonesty for those sharing their code as for those
using other’s code. As was explained in class, never use or share code! If you wish to help another
student, explain concepts in English, draw diagrams, or refer the student to specific reference material.
Similarity detection software will be used on all assignments. Any students who achieve a high score for
improbable code similarities will receive a mark of 0. In addition, further Academic Dishonesty reporting
may be performed.
Classes to Submit: Do NOT zip your files, or submit any additional files! You will lose marks!
 MazeSolverToo.java
 PriorityNode.java
Exceptions
Your code must correctly handle thrown exceptions. To handle the exceptions you need only to inform
the user through a console print statement what specifically has happened. These handlers must be
specific (rather than one catch block for Exception itself). Be sure to be mindful of exception
superclasses/subclasses.
Command Line Arguments
You must read the Maze file from the command line. The command line is what computers used to use
to run programs rather than having graphical windows, and all systems still have the functionality
available (like through the Terminal application on Macs, or the Command Prompt (cmd) application
on Windows). The user could run the MazeSolverToo program with the following command from a
command line (for example): java MazeSolverToo maze1.txt
If you have ever wondered what the “String[] args” thing meant in the main method header, this
is what it is for; It allows us to read in the text supplied on the command line. The args array of Strings
will store any of the text supplied by the user, that is, any tokens following the application name
(MazeSolverToo in the above example).
To read a single argument, we look in args[0], but first we want to check that the user has entered
something. The following code example could be the beginning of your MazeSolverToo.java file. It
will check the length of the args array and thrown an exception if there is not an argument provided.
Then it will store a reference to the String using the reference variable mazeFileName.
public class MazeSolverToo {
public static void main (String[] args) {
try{
if(args.length<1){
throw new IllegalArgumentException(“No Maze Provided”);
}
String mazeFileName = args[0];
//…
Setting up a Command Line Argument when running your program in Eclipse
To get Eclipse to supply a command line argument to your program when it runs, you will need to
modify the “Run Configurations”. On my computer it’s located in “Run”->”Run Configurations”.
Something like the following should pop up.
Be sure the “Java Application->MazeSolverToo” (note, picture only says ‘MazeSolver’) is the active
selection on the left-hand side.
Select the “Arguments” tab.
Enter the filename and location in the “Program arguments” text box. In my case I have it in
“C:\Users\Jason\CS1027\fall2017\assignment3\maze0.txt”, however you may have it somewhere
completely different and that is to be expected.
If you are on Mac/Linux you will likely have something like
“/Users/SomeName/Desktop/Ass3/maze2.txt”.
FAQ:
 Q: I don’t know where to start.
o A: Did you read the whole assignment details?
 Q: I still don’t know where to start.
o A: Go over the high level description of the algorithm. It really does into the details of
solving the problem. You should also make sure you’re comfortable with the provided
classes – read the documentation provided.
 Q: I don’t know what A* is.
o A: Read this. For real, read it! If you’re still lost, check out YouTube, I’m certain there
are videos there describing it.
 Q: Should I comment X?
o A: Probably.
 Q: There is a bug in my code!
o A: Look at the debugging lecture slides. There are a lot of tips in there.
 Q: Am I required to make any alterations to any of the provided code?
o A: No, you shouldn’t have to.
 Q: Did I catch enough exceptions?
o A: No idea. Keep trying to figure out how to break your code. Make sure you have at
least 4 being dealt with.
 Q: Can I change the specifications, even if it’s to make it ‘better’?
o A: NO! Not even if you invent the best maze solver in the world.
 Q: When catching exceptions, does order matter?
o A: Yes, it does actually. Remember subclasses are also the same type of parent classes.
 Q: I swear I did everything right, but for some reason my files won’t open!
o A: This isn’t uncommon.
 If you’re using eclipse, try putting the .txt files in the project directory (the same
folder containing the bin folder, src folder.
 If you’re running from command line, try putting the files in the src folder.
 Q: I don’t know how to do X?
o A: Try going to my favorite website: www.google.ca and then typing X into the big text
box.
 Q: Can I email the TA or professor with questions?
o A: Yes, but you should really check out my favorite website (above).
Non-functional Specifications:
1. Include brief comments in your code identifying yourself, describing the program, and describing
key portions of the code.
2. Assignments are to be done individually and must be your own work. Software will be used to
detect cheating.
3. Use Java coding conventions and good programming techniques, for example:
i. Meaningful variable names
ii. Conventions for naming variables and constants
iii. Use of constants where appropriate
iv. Readability: indentation, white space, consistency
v. private vs. public
Make sure you attach your files to your assignment; DO NOT put the code inline in the textbox. DO
NOT SUBMIT YOUR .class FILES. IF YOU DO THIS, AND DO NOT ATTACH YOUR .java
FILES, YOU WILL RECEIVE A MARK OF ZERO!
What You Will Be Marked On:
1. Functional specifications:
 Does the program behave according to specifications?
 Does it run with the main program provided?
 Are your classes created properly?
 Are you using appropriate data structures?
 Is the output according to specifications?
2. Non-functional specifications: as described above
3. Assignment submission: via OWL assignment submission

CS1027: Assignment 3
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