90-771 Data Structures and Algorithms Project 5
Carnegie Mellon University
90-723 Data Structures and Algorithms Page 1 of 9
95-771 Data Structures and Algorithms for
Information Processing Project 5
Project 5 LZW due Wednesday, December 7!at!11:59:00!PM
Warning: This assignment will take a little longer than the others that we have done. Please have
plenty of questions ready for next week’s class.
Topics: Lempel-Ziv Welch Compression
Write a Java implementation of the Lempel-Ziv Wech compression algorithm. Your
program will be able to compress and decompress ASCII and binary files.
Run your solution to compress and decompress shortwords.txt (on the schedule).
After testing on shortwords, run compress and decompress on words.html (also on
schedule but much larger than shortwords.txt). For another text file, run your
solution on CrimeLatLonXY1990.csv (on the course schedule).
For the binary test case, be able to compress and decompress the video on the
schedule (01_Overview.mp4). This is a video that I created for another course. You
are not responsible for the material in this video. But you do need to be able to
compress it and decompress it. Simply download it to your own system and use it as
a data file for your LZW solution.
When LZW compression calls for the use of a table, you will use a hash map. This
hash map will be implemented with an array of linked lists. You need to write your
own hash table and supply your own linked list. The array will provide for 127 linked
lists (indexes from 0 to 126). The design of the linked list data field is in your hands.
Note that there are two distinct types of searches going on in LZW. On the one hand,
we want to store strings so that we can later look them up and find their
correseponding 12-bit values (for LZW compression). On the other hand, we are
presented with a 12-bit code word and need to quicky find the corresponding string
(for LZW decompression). Your array of linked list is appropriate for putting and
getting a value based on a string key. A simple array is appropriate for quickly
retrieving a string given a 12-bit key. We will not be using Java’s HashMap or
TreeMap classes in this program.
In order to execute your program for compression the user will type the following:
java LZWCompression -c shortwords.txt zippedFile.txt
And to decompress the program is run with the following command:
java LZWCompression -d zippedFile.txt unzippedFile.txt
In this example, unzippedFile.txt now has the exact same contents as
shortwords.txt.
