CSCI 151 - Lab9: The Kevin Bacon Game

Due on Thursday, May 26 (the last day of classes)

You may work with a partner on this assignment.

Introduction

For this lab you will write a program that allows you to play the "Kevin Bacon Game". A person's "Bacon Number" is computed based on the number of movies of separation between that person and the actor Kevin Bacon. For example, if you are Kevin Bacon, then your Bacon Number is 0. If you were in a movie with Kevin Bacon, your number would be 1. If you weren't in a movie with Kevin Bacon, but were in a movie with someone who was, your Bacon Number would be 2. In short, your Bacon Number is one greater than the smallest Bacon Number of any of your co-stars. We will make use of data tables from the Internet Movie Database to calculate Bacon Numbers.

For fun and some additional background, you can try out the Oracle of Bacon at the University of Virginia.

There is starter code for this lab. Make a new project folder Lab9<LastName>. Download and unzip Lab9Start.zip into the new project folder before you start up Eclipse. Then make a new Lab9 project and away you go.

Program Organiization

To save you some time and to keep everyone on the same structure, I am giving you some files with starter code:

Files Edge.java and Vertex.java are essentially the same as the files we used in class for other graph structures. You need to add to Vertex.java an integer variable distance that represents the node's distance from the source vertex and a Vertex variable predecessor that gives the node's predecessor in the chain back to the source.. You shouldn't need to make any changes in the Edge.java file.
File Graph.java has two incomplete methods that represent the bulk of your work for this lab. One method is loadFile(String fName). This loads the IMDB data from a file and builds a graph from it. Note that I have given you code that allows you to use cloud data as well as data files on you computer -- thse IMDB files are larage -- up to 300MB, so you don't necessarily want to download them and we certainly don't want you to hand them in.
The other method you need to write for Graph.java is findAlllPaths(String s) which finds the shortest path from each node in the graph to the "source node" whose name is s. This algorithm shoud assign values to the distance and predecessor variables you added to Vertex.java.
Finallly, you need to go back to the Vertex.java class and add the method getPath( ). This returns a string showing how to go from the source node to the given Vertex. For example, if the source node is "A" and the path from "A" to "D" goes through nodes "B" and "C" this might return "A => B => C => D".
File MakeGraph.java should not need any changes. This sets up a dialog with the user that calls the methods of the other files. MakeGraph expects a command-line argument args[0] to be the name of a data file; if you want to change data files you need to re-run the program. Here are the commands the user can enter:
Connect: the user is asked the name of the source node and the findAllPaths method is run on this name.
Path: the user is asked for the name of any node in the graph and the getPath method is run on the Vertex corresponding to this name.
Actors: this lists all of the actors connected to the current source and their Bacon numbers (which are half of their distances from the source)
Movies: this lists all of the movies connected to the current source
Refresh: This clears all data set by the findAllPaths so you can connect to a different source

File Format and an Example

The movie data file contains information on what movies a performer appears in. Every line contains information on one person appearing in one movie. The lines are formatted as follows:

    <performer name>|<movie title>

The vertical pipe character '|' can be used to determine where the name ends and the title begins. There will only be one '|' on a line and there are no empty names or titles. The Java String class has a number of methods that can be used to divide up the line. One easy way to do this is to scan a line of the file into String line, let int b be line.indexOf( '|') and to split the line into two substrings: one before b and one after b.

To help you debug your program I have given you one non-IMDB file called "Simple.txt". Here is the complete contents:

   A|One
   A|Two
   A|Three
   B|Two
   C|Three
   C|Four
   D|Four
   D|Five
   E|Five
   F|Five

Here A, B, C, D, E, and F are actors and One, Two, Three, Four, and Five are movies. You want your program to build the following graph:

Note that for every line A|B in the file you will create two edges: one from node A to node B, and one from B back to A. Your findAllPaths( ) method using node A as the source will add to this the following edges, shown in red:

The distance variable you use in this method assigns as the distance for each node the number of red edges between it and the source: A has distance 0, B has distance 1, C has distance 2, and so forth. The actors all have even distance, the movues akk have odd distance. This allows you to add each Vertex to either the availableActors list or the availableMovies list when you assign its distance.

Data Files

The zipped file of starter code has some smaller data files. Note that in each of the IMDB files Kevin Bacon is referred to as "Kevin Bacon (I)".

Simple.txt is the 10-line file shown in the example above.
imdb.small.txt has 1817 lines. Kevin Bacon is connected to 160 actors in 1586 movies.
imdb.top250.txt This has 14,338 lines. Kevin Bacon is connected to 11,802 actors in 233 different movies.

I have also posted with the lab

imdb.no-tv.txt This has over 5 million lines. Kevin Bacon is connected to over 1.6 million actors in 438,953 movies. This is well over 200 megabytes; don't download it. You can access it as "http://cs.oberlin.edu/~bob/cs151/Labs/Lab9/imdb.no-tv.txt".

Handing In

Please delete all of your ".txt" data files. Look through your ".java" files and make sure you've included your name (and your partner's name if you worked with a partner) at the top of all of them. You should have four class files: Vertex.java, Edge.java, Graph.java and MakeGraph.java.

Include in your submission a file named README. The contents of the README file should include the following:

Your name and your partner's name if you worked with someone
A statement of the Honor Pledge
Any known problems with your classes or program

As usual, make a zipped copy of you project folder (which should be Lab9<your last name>) and hand it in on Blackbard as Lab9.

Acknowledgments

Information courtesy of The Internet Movie Database (http://www.imdb.com/). Used with permission. The data should only be used for personal and non-commercial purposes.