Description

Important Notes:
1. The assignment is an individual project, to be finished on one’s own effort.
Marking Criterion:
1. The full score of the assignment is 100 marks.
2. Normal submission: 100 marks are given if a submission passes both compression and decompression tests. 80 marks are given if it passes compression test only.
3. Resubmission: For normal submissions that fail in compression test, a resubmission is allowed within one week after the marking. 60 marks are given if the resubmission passes compression test. 75 marks are given if the resubmission passes both compression and decompression tests.
4. Late submission: 60 marks are given if the submission passes compression test. 75 marks are given if it passes both compression and decompression tests. No resubmission is allowed.
5. Zero mark is given if: there is no (normal or late) submission; a normal submission fails compression test and the resubmission fails compression test; a normal submission fails compression test and there is no resubmission; a late submission fails compression test.
Running Environment:
1. The submissions will be evaluated in Java environment under Linux platform.
2. The submission is acceptable, if it runs in any of recent versions of Java SDK environment. These versions include from Java SE 8 to the most recent Java SE 17.
3. The submission is only allowed to import three packages of (java.lang.*; java.util.*; java.io.*) included in Java SDK. No other packages are allowed.
4. In each test, the program is required to finish within 5 second of time, with no more than 128MB memory.
5. Each student is free to test his/her program in the evaluation platform before the submission.
Submission Guidelines:
1. Detailed submission guideline will be given in a separate manual around Nov. 15.
2. Inconsistency with or violation from the guideline leads to marks deduction.
Functional Requirement:
This assignment implements the Huffman tree (https://en.wikipedia.org/wiki/Huffman_coding), which is a powerful algorithm widely in data compression. Two programs are required.
1. HuffmanCompression.java compresses a given text file (encoded with ASCII code) using Huffman tree method with the following command:
java HuffmanCompression input.txt dictionary.txt compressed.txt

An example of input file follows:
input.txt (note: there is a linefeed symbol at the end of the following sentence)
SUSIE SAYS IT IS EASY

After constructing a Huffman tree, one file of code dictionary will be output:
dictionary.txt
10:01110
32:00
65:010
69:1111
73:110
83:11
84:0110
85:01111
89:1110
The dictionary shows that the space character will encoded as “01110” (note that 10 is the ASCII code of the linefeed character. 32 is the ASCII code of the space character…)

The other output will be the compressed text:
compressed.txt
11011111111011110011010111011001100110001101100111101011111001110
The file gives the compressed text of the input.txt based on the dictionary shown above.

2. HuffmanDecompression.java decompresses a compressed text based on the Huffman code dictionary with the following command:
java HuffmanDecompression compressed.txt dictionary.txt output.txt

The compressed.txt and dictionary.txt are input files obtained from the compression process. The output file (“output.txt”) should have the same contents as “input.txt” used in the compression process.

Program Template:
Each submission is expected to strictly follow the template to implement the required function.
1. Modify getHuffmanCode() and getCompressedCode() in HuffmanCompression.java to implement the required compression function.
2. Modify main() in HuffmanDecompression.java to implement the required decompression function.

Appendix
1. HuffmanCompression.java
2. HuffmanDecompression.java
3. input.txt
4. dictionary.txt
5. compressed.txt
6. output.txt