README.md

Instructions

• Clone the repository, or download the zip file and unzip it.
• Run the command mvn package.
• This will build the project, create a JAR file in the targets/ folder and run all tests.
• Opening the project folder in IntelliJ as a project will also enable running the tests and inspecting the code.

API Functions

The API is contained in the GraphData.java file at src/main/java/ location. The various functions implemented are listed below:

• boolean parseGraph(String filepath) : Import DOT file to create a JGrapht graph object. Returns true if successful else false.
• String toString() : Display graph information such as node and edge number in string format. Returns a String.
• boolean outputGraph(String filepath) : Writes graph details to a file at filepath. Returns true if successful else false.
• boolean addNode(String label) : Adds a node to the graph. Returns true if successful else false.
• boolean addNodes(String[] labels) : Adds a list of nodes to the graph. Returns true if successful else false.
• boolean addEdge(String srcLabel, String dstLabel) : Adds an edge to the graph. Returns true if successful else false.
• boolean outputDOTGraph(String path) : Outputs the JGraphT graph object to a DOT file at the specified path. Returns true if successful else false.
• void outputGraphics(String path, String format) : Outputs the JGraphT graph object to a file with file format format at the specified path.

How to use (Example code)

• GraphData object creation

GraphData graphApi = new GraphData();  

• Parse a graph

graphApi.parseGraph("src/main/resources/example.dot");

Expected Output: ![[Pasted image 20231011191820.png]]

• Display graph data

graphApi.toString();

Expected Output:

Number of nodes: 4  
Node labels: [A, B, C, D]  
Number of edges: 3  
Node and edge directions: (A -> B), (A -> C), (A -> D)

• Output graph data to file

graphApi.outputGraph("src/main/resources/output.txt");

Expected Output (in output.txt):

Number of nodes: 4  
Node labels: [A, B, C, D]  
Number of edges: 3  
Node and edge directions: (A -> B), (A -> C), (A -> D)

• Add nodes

graphApi.addNode("Y");
graphApi.addNodes(new String[]{"Z", "X"});

• Add edge

graphApi.addEdge("Z", "C");

• Output graph in DOT file format

graphApi.outputDOTGraph("src/main/resources/gen_graph.dot");

Expected Output (in gen_graph.dot):

strict digraph G {  
A;  
B;  
C;  
D;
Y;  
Z;
X;  
A -> B;  
A -> C;  
A -> D;  
Z -> C;  
}

• Output graph as PNG file

graphApi.outputGraphics("src/main/resources/", "png");

• GraphSearch API

Path path = graphApi.GraphSearch("C","D", Algorithm.BFS); 
// Algorithm.DFS can also be used.
path.printPath();

Expected Output

Using BFS
C->A->D

Project Part 3

Refactors

• refactor: Encapsulate graphObject and create a getter function. This refactor commit aims to encapsulate the graphObject object by making it private to the GraphData class. A getter function called getGraph is now used to safely access the object.
• refactor: Rename opt variable to graphString. The variable name 'opt' does not provide a good idea about its purpose, so I rename it to graphString to make it clearer.
• refactor: Convert test filepaths to static final variables. This commit converts test filepaths to static final variables. This helps to organise the test parameters a bit more easily.
• refactor: Add nullcheck in printPath function. This commit aims to avoid a NullPointerException by adding a null check to the function printPath.
• refactor: Add comments in multiple functions This commit introduces comments at various parts of the codebase to explain written code better.

Template Pattern

The Template Pattern involves:

• Creating an abstract class (GraphSearch) to define common graph search steps.
• Extending this template with concrete subclasses (BFS and DFS) that implement specific traversal methods by overriding abstract template methods.
• This structure provides a shared algorithm skeleton while allowing BFS and DFS to have their unique implementations.

Strategy Pattern

The Strategy Pattern involves:

• Defining a strategy interface (SearchStrategy) that declares a method signature for the algorithm.
• Creating concrete strategy classes (BFS and DFS) that implement the strategy interface with their specific algorithm implementations.
• Implementing a context class (Context) that holds a reference to the strategy interface and utilizes it to execute the selected strategy.
• Utilizing the Context class in the main code to dynamically switch between different strategies (BFS or DFS) based on input.

Random Walk Search

Exampe graph (from Canvas) ![[Pasted image 20231203183455.png]]

Running this code,

Path path = graphApi.GraphSearch("a","c", Algorithm.RWS);  
path.printPath();

gives the following outputs - ![[Pasted image 20231203183730.png]] ![[Pasted image 20231203183757.png]] ![[Pasted image 20231203183807.png]]

Commits

main

• Initial commit
• Add maven pom file.
• Update pom file.
• Implement first feature.
• Implement second feature.
• Implement third feature.
• Implement fourth feature.
• Handle IO exceptions.
• Add tests
• Update pom file.
• Update readme.
• Create maven.yml for buld automation.
• Update maven.yml to Java 21
• Add features to remove nodes.
• Add exception throws to functions.
• Add features to remove edges.
• Update maven.yml
• Add Path class.
• Add GraphSearch API with BFS algorithm.
• Add bfs GraphSearch tests.
• Add GraphSearch API with DFS algorithm.
• Add dfs GraphSearch tests.
• Merge commit.

bfs

• Add GraphSearch API with BFS algorithm.
• Add bfs GraphSearch tests.

dfs

• Add GraphSearch API with DFS algorithm.
• Add dfs GraphSearch tests.

refactors

• refactor: Encapsulate graphObject and create a getter function.
• refactor: Rename opt variable to graphString.
• refactor: Convert test filepaths to static final variables.
• refactor: Add nullcheck in printPath function.
• refactor: Add comments in multiple functions

Template & Strategy patterns

• Implement template pattern for graph search algorithms.
• Add strategy pattern to graph search functionality.

Random Walk Search

• Add Random Walk search algorithm as option.

PR Review commits

• Extract getPath function to template class.
• Add random walk search tests.
• Add input test dot file for RWS test.