Project 2 - The search for a-MAZE-ing donuts!

Phase A

Important Deadlines

Project released	Fri. Jan. 18
Partner selection	Wed. Jan. 23	Notify instructor by email by 10 pm
Phase A Due	Wed. Jan. 30	Electronic turnin by 11:00 pm using this online dropbox, (not that we recommend waiting until the last minute...) (no paper turnin)
Phase B Due	Wed, Feb. 13	Electronic turnin by 11:00 pm, Paper turnin beginning of Quiz Section on Feb. 14

IIIa. Phase A: Stacks, Queues, and PQueues

Code requirements
README Questions (look at this before starting)

IIIb. Phase B (brief description): Running the maze

IV. Logistics: Teams
V. Phase A Provided Code
VI. Phase A Turnin

I. Introduction

It is an incredibly serendipitous day for you at the Paul Allen Center. A mysterious bearded benefactor has appeared during the night and has left behind donuts for the entire CSE 326 class! You've managed to get out of bed at a yawningly-early 10 AM, meaning you have first dibs on all the yummy goodness of fresh-baked donuts if you can get to them in time (and the always hungry grad students from the night before haven't beat you there). Unfortunately, the Allen Center space czars just happened to have decided to rearrange all the furniture during the night (as part of their experimentation with different settings in the new building), turning the entire building into one complex and mystifying maze. You haven't had your morning coffee yet, and you just don't feel like running around looking for donuts-- but you're so hungry! Why not let your computer solve the maze and find the donuts FOR you?

II. Learning Objectives

In this assignment, you will:

Work on the PriorityQueueADT, and implement your own data structures.
Gain experience with systematic testing.
Explore the similarities and differences between recursive and iterative algorithms.
See an application of the Stack, Queue, and PriorityQueue ADT's in maze search.
Gain experience analyzing an existing codebase's architecture, and modifying existing code.
Train your computer to do your most important tasks for you -- like finding donuts!

III. Assignment and Algorithm Overview

For the complete assignment, you are required to write several new maze-solving MazeRunner classes. There should be one MazeRunner class for each of the following algorithms (subject to change in Phase B instructions):

Iterative Depth-First Search (DFS) -- please implement this search with a Stack
More information on DFS can be found here.
Breadth-First Search (BFS) -- please implement this search with a Queue
More information on BFS can be found here.
Best-First Search (not abbreviated for obvious reasons) -- please implement this search with a ThreeHeap (i.e. a d-Heap where d = 3)
More information on Best-First Search can be found here.

IIIa. Phase A: Stacks, Queues, and PriorityQueues

Description

In Phase A of this assignment, you will be writing code that implements a given (new) interface for a stack, queue, and priority queue (2 implementations). You should test these implementations to be sure they are correct before proceeding to Phase B (posted next week). In particular, you are required to design and implement a collection of JUnit tests that verify that your code works properly.

Code Requirements

Your task for Phase A is to:

Implement a stack, queue, a binary heap, and a three-heap according to the interfaces provided. Your implementations should automatically grow (if interested you may also make them shrink - this is optional) as necessary. Note: Growing an array implementation one element at a time is not likely to be the most time efficient solution, if you use arrays, try to come up with a more time-efficient solution. You may reuse any code you wrote for Project #1 for this purpose but be sure that you implement the interfaces provided for this project. Make a separate file for your stack implementation (MazeStack.java), your queue implementation (MazeQueue.java), your binary heap implementation (BinaryHeap.java), and your three-heap implementation (ThreeHeap.java). The heaps should be implemented with arrays; you are free to implement the stacks and queues as you wish, although arrays are as simple as anything. (Although our usual rule prohibiting use of the Java class libraries to do the actual work remains).
Implement unit tests for your stack, queue, and priority queue heaps using JUnit, and verify that your code passes the tests. Your tests will be evaluated on how comprehensive your test coverage is, and whether tests are small and modular. But note that good test coverage is not synonymous with having lots of tests that are fundamentally the same. (Hint: You may be able to reuse a single suite of tests for both implementations of the priority queue if you think about how to take advantage of interface types and maybe inheritance in the test code. Massive cut-'n-paste is not as good an alternative.)
You should also take this opportunity to get an understanding of how the three graph search algorithms described here work for a general graph.

README.TXT Questions

You should turn in a README file with an informal description of your test plan. Summarize the tests you implemented and explain how they provide comprehensive test coverage for your classes. This should not just be a dump of the test names and comments from the code file - we can read that. What we want is to get an idea of the thinking behind what you did.

IIIb. Phase B: Running the Maze (more later)

Phase B will involve implementing the above tree traversal algorithms (they will be implemented as MazeRunner classes), understanding operations on a maze as a graph, and analyzing and extending the maze code which we will provide.

IV. Logistics: Teams

You are encouraged (although not required) to work with a partner of your own choosing for this project. You may choose how to divide the work between the two of you under three conditions:

1. You must document each team member's effort in the README file (record this now so you have the info for the phase B readme file);

2. Work together so that you both understand your answers to the questions answered in the README (for Phase B);

3. Understand (at least) at a high level how your team member's code is structured and how it works (code for both Phases A & B).

If working with a partner, you must find your partner and send a single email to the instructor with the name AND UW email id of both partners by the deadline given at the top of this document. If you are planning on working alone, you should also email the instructor a message stating “I am working alone”.

Remember to test your team's code as a whole to make sure that your portions work together properly! Also, be aware that except in extreme cases and provided you notify us in advance of the deadline, all team members will receive the same grade for the project.

If you would like to use a shared group directory, please contact one of the TA's for instructions. This is NOT necessary, just optional if it is your preference.

V. Phase A Provided Code

To facilitate understanding of this rather complex project, and to encourage good modular decomposition and "unit testing" (testing small pieces of code instead of testing the entire program all at once), this project is broken into two Phases. For Phase A, we suggest improving and testing your basic "helper" data structures (i.e. Stack, Queue, BinaryHeap, ThreeHeap) without worrying about the Maze-related code.

For this first Phase, we are providing the interfaces for a Stack, a Queue, and a PriorityQueue. You must write an implementation of the Stack and Queue interface as described above. In addition, you must write two implementations of the PriorityQueue interface – a BinaryHeap and a ThreeHeap. (For the ThreeHeap we suggest starting with a copy of your BinaryHeap code and making changes as necessary, although making the original code easy to generalize may save you time in phase B (hint, hint).).

Java code: Right-click on the links below to download the starter code.

PriorityQueue.java -- interface for a PriorityQueue ADT. Both BinaryHeap.java and ThreeHeap.java should implement this..
Stack.java -- interface for a Stack ADT.
Queue.java -- interface for a Queue ADT.

Your priority queue implementations must accept Comparable objects. Many classes such as String and Integer implement the Comparable interface. In Phase B you will need to modify/create some more classes that implement the Comparable interface (in other words, writing your own compareTo method). Then you will be able to have priority queues containing those objects. Unlike your stacks implementations for Project1 that were hardcoded to use doubles, your implementations of the Stack, Queue, and PriorityQueue interface need to use generics. Your implementations of BinaryHeaps and ThreeHeaps in particular need to use compareTo when comparing elements so the code will work on any Comparable object. More information about Java's Comparable interface may be found at Sun's website. In addition, you might find this description from Fall 2006 cse143 to be useful. Both generics and the Comparable interface are discussed in section 1.5 of the Weiss text, and there is a good tutorial on Sun's web site. The tutorial is based on this paper by Gilad Bracha, one of the Java language designers.

For Phase B of this project, we will be providing additional code which will read, parse, and build a Maze class object from a text file. We will also give a simple MazeRunner class from which you can inherit your own MazeRunners.

VI. Phase A Turnin

Phases A and B will be graded together when your entire assignment is turned in with Phase B. However, 15% of your grade will be based upon the "in-progress" checkin for Phase A. Although 15% is a relatively small fraction, you are highly encouraged to successfully complete all of Phase A by this deadline, as there is much more work to do in Phase B.

We will be testing the code that you submit for the in-progress checkin - so we will expect that you have done the same!

Only one person from each team should submit. The same person should submit both Phases A and B. You should submit all of the Java code you wrote: MazeStack.java, MazeQueue.java, BinaryHeap.java, and ThreeHeap.java.