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diff --git a/src/dk.biks.bachelorizer/dk/biks/bachelorizer/Combi.java b/src/dk.biks.bachelorizer/dk/biks/bachelorizer/Combi.java
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+// SPDX-FileCopyrightText: 2025 Jonas Smedegaard <dr@jones.dk>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package dk.biks.bachelorizer;
+
+import java.util.Collection;
+import java.util.Set;
+
+import com.example.portfolio3.AdjListGraph;
+import com.example.portfolio3.Graph;
+import com.example.portfolio3.GraphAlgorithms;
+import com.example.portfolio3.MatrixGraph;
+import com.example.portfolio3.Vertex;
+
+/// Combi - static sample dataset of course combinations
+///
+/// Slurps and parses data from upstream-provided comma-separated file.
+///
+/// @version 0.0.1
+/// @see <https://moodle.ruc.dk/mod/assign/view.php?id=523186>
+public final class Combi {
+
+	/// data about combinations as a Graph
+	private Graph g;
+
+	/// Default constructor
+	///
+	/// @param path  path to data file
+	private Combi(final String path) {
+
+		// read into temporary graph to resolve vertice count
+		//
+		// use Adjacency List Representation:
+		//  * cheap to bootstrap (done once)
+		//  * simple to count vertices (done once): O(1)
+		Graph _g = new AdjListGraph();
+		GraphAlgorithms.readGraph(_g, path);
+		Integer _vertice_count = _g.vertices().size();
+
+		// read into final graph
+		//
+		// use Adjacency Matrix Representation:
+		//  * expensive to bootstrap (done once)
+		//    * simple to add edges but needs vertice count
+		//  * simple to get edges (done repeatedly): O(1)
+		//
+		// TODO: avoid reading and parsing file twice
+		Graph g = new MatrixGraph(_vertice_count);
+		GraphAlgorithms.readGraph(g, path);
+
+		// ensure the graph is connected
+		isConnected(g);
+
+		GraphAlgorithms.printGraph(g);
+
+		// release temporary variables for garbage collection
+		_g = null;
+		_vertice_count = null;
+	}
+
+	/// JVM entry point
+	///
+	/// @param args  command-line arguments
+	public static void main(final String[] args) {
+
+		// first argument, if provided, is the data file path;
+		// else use upstream named file in current directory.
+		String path = (args.length > 0)
+			? args[0]
+			: "combi.txt";
+
+		Combi combi = new Combi(path);
+	}
+
+	/// utility function to check that a graph is connected
+	///
+	/// If check fails, throw an unchecked exception,
+	/// since it occurs at runtime and is unrecoverable.
+	///
+	/// Time complexity of the operation is O(n²)
+	/// where n is the amount of vertices,
+	/// since visitDepthFirst() recurses out-edges of all vertices.
+	///
+	/// @param g  Graph to inspect
+	/// @throws IllegalArgumentException
+	/// https://docs.oracle.com/javase/tutorial/essential/exceptions/runtime.html
+	public static void isConnected(Graph g) {
+
+		// collect all vertices in the graph
+		Collection<Vertex> c = g.vertices();
+
+		// pick a random vertice in the graph
+		Vertex v = g.vertices().iterator().next();
+
+		// collect the set of visitable vertices
+		Set<Vertex> visited = GraphAlgorithms.visitDepthFirst(
+			g, v);
+
+		// throw exception if not all vertices were visited
+		if (visited.size() != c.size()) {
+			throw new IllegalArgumentException(
+				"graph is not connected");
+		}
+	}
+}