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Data Structures and Algorithms

Source code plagiarism

In this project, we create 3 algorithms for analysing source code plagiarism.

  • Naive algorthim condenses code logic to the root node, drawing inspiration from merkle root. We compare trees by the root node. (Scalability)
  • Snapshot algorithm looks at each tree breadth-wise and depth-wise to analyse code similarity. We use frequency analysis to give inverted weights to each node type for a more nuanced score. Weights are based on fibonacci sequence, which highlights differences (~60%) and reduces noise in the similarity comparison. (Accuracy)
  • Progressive algorithm compares two trees, iteratively exploring each tree level. (Efficiency)

Main data structures used are abstract syntax trees, hashmaps, linked lists and arrays. Dataset taken from IEEE Dataport: https://ieee-dataport.org/open-access/programming-homework-dataset-plagiarism-detection#files.

Useful Directories:

"codes/src/main" directory -> Contains maven project for 3 algorithms.

1. Naive implementation
2. Snapshot implementation 
3. Progression/Dynamic implementation

"c-to-json" directory -> contains c code from https://github.com/deiuch/c-to-json

=> To convert C language codes to ASTs(Abstract Syntax Tree) in the form of JSON.

"codes/data" directory -> EDA (Exploratory Data Analysis) of our dataset

=> Segregation of datasets into small, medium and large file sizes.

"codes/helper" directory -> To aid in the count of the number of characters in each file

=> To perform EDA for the datasets.

Installation for code running.

Intellij (/codes directory)

Import the project and press the play button.

MAVEN

pip install maven
cd codes
mvn compile
mvn exec:java  -D"exec.mainClass"="copycat.Application"

Usage for "c-to-json"

For linux/ubuntu

cd c2json
sh parse.sh

Specify the c file you wish to convert and the directory it is found at.

For windows

Download WSL

Future extensions

  • To allow for comparisons of entire repos, not just single-file source code.
  • To allow for analysis of larger source code, which would require progressive algorithm to build compare the trees iteratively instead of having the requisite of --having the entire tree built in-memory.
  • To allow for multiple comparisons usin indexing, which would build on the naive merkle-root algorithm.
  • To highlight plagiarised portions through a UI.

Limitations

Plagiarism is subjective. There is still need for manual review of each code on a case by case basis.

Video

https://www.youtube.com/watch?v=t68WSdoI_Do&feature=youtu.be

Contributing

Job Seow, John Luke, Kenneth Kho, Wen Yu, Christopher Lim

License

MIT