COSC 2010 / 2100 Data Structures

Fall 2014

Homework Assignment #1 : Magnetic Chameleon

Due: Wednesday, September 3rd, Noon CDT
Submit: Turn in your MagneticChameleon.java source file using the turnin command on morbius.mscs.mu.edu. Work is to be completed individually. Be certain to include your name in the file. You may submit multiple times, but only the last turnin will be kept. The automatic submission system will not accept work after the deadline.

GridWorld

The Advanced Placement GridWorld Case Study is a useful starting point for this semester's warm-up assignment.

Begin by downloading GridWorld code, as well as the Student Manual for your reference.

The Eclipse Integrated Development Environment and Java are already installed on the laboratory machines. If you would like to use another computer to do your work, it is your responsibility to ensure that the necessary software is installed.

Online resources (such as this YouTube video) can help you get started with setting up the GridWorld JAR file under Eclipse, in order to beginning running the sample projects.

For this assignment, you will be implementing your own extension of an existing GridWorld class to simulate the MagenticChameleon.

Magnetic Chameleon

GridWorld already contains a variety of Actors that can inhabit the grid: Bugs, Flowers, Rocks and Critters. This assignment will only be concerned with Rocks and Critters.

The existing ChameleonCritter example class (GridWorldCode/projects/critters/ChameleonCritter.java) moves randomly about the board, one square at a time, changing its color to match adjacent Actors.

Create a new Critter type, MagneticChameleon, the detects another MagneticChameleon on the grid, and attempts to move toward it on each step. If it reaches the other MagneticChameleon, it should take on the same orientation, and change its color to be halfway between its previous color and the new neighbor's color.

Unlike ChameleonCritters, MagneticChameleon should ignore any other Actors on the grid. Like ChameleonCritter, MagneticChameleon should not pass through any Rocks in its way.

If an obstacle (Rock) occupies the square that a MagneticChameleon wants to step into next, it should instead choose an unoccupied square that is closest to the direction of the other MagneticChameleon. If there is a tie between squares when it is selecting its next move location, it should default to the choice in the direction it is already going.

Testing

Points for this assignment will be awarded based upon successful completion of a battery of testcases. As you might guess, test scenerios will generally consist of placing two MagneticChameleons of various starting colors at various locations on the board, with diverse patterns of Rocks between them.

You should create many of your own testcases, (see GridWorldCode/projects/critters/ChameleonRunner.java as an example,) but we will only evaluate your MagneticChameleon.java source file.

• Name your class precisely -- spelling and capitalization must match this assignment specification for you to pass any of our testcases.
• Do not modify any of the other GridWorld classes -- or, at least, do not make your solution depend upon any modifications you make to other GridWorld classes. Your MagneticChameleon.java source file will be graded in a fresh copy of GridWorld, with our own test framework, by the TA-bot.
• Make certain that your code compiles correctly -- no points can be awarded if your submission will not run to pass any of the testcases.
• If you put any debugging System.out.println() statements in your code during development, please comment these out before submission. Stray output from your program will confuse TA-bot.

Extensions

If you complete this assignment quickly, you might like to think about variations on the problem. Do not turn these in -- many will break TA-bot's grading testcases -- but do give them some thought:

• It's not hard to come up with a configuration of rocks that prevents the MagneticChameleons from reaching each other, even though open paths on the board exist. What modifications could you make to MagneticChameleon's guidance algorithm to guarantee that it would explore all possibilities?
• Even with a better guidance algorithm, are there still solvable boards where the MagneticChameleons never connect? (Imagine, for example, a situation where both of them circle around an obstacle, but never rendezvous.) Why, or why not?
• How does your implementation behave if more than two MagneticChameleons are placed on the board?