DIMACS IO Implementation

jgalgo-io/src/main/java/com/jgalgo/io/FormatDIMACS.java

@@ -15,15 +15,21 @@
  */
 package com.jgalgo.io;
 
+import java.io.BufferedReader;
+import java.io.IOException;
 import java.io.Reader;
+import java.io.UncheckedIOException;
 import java.io.Writer;
 import java.util.List;
+
 import com.jgalgo.graph.Graph;
 import com.jgalgo.graph.GraphBuilder;
+import com.jgalgo.graph.Weights;
 
 class FormatDIMACS implements GraphFormat {
 
-	private FormatDIMACS() {}
+	private FormatDIMACS() {
+	}
 
 	static final FormatDIMACS Instance = new FormatDIMACS();
 
@@ -48,18 +54,157 @@ private static class WriterImpl implements GraphWriter {
 
 		@Override
 		public void writeGraph(Graph graph, Writer writer) {
-			// TODO Auto-generated method stub
-			throw new UnsupportedOperationException("Unimplemented method 'writeGraph'");
+			try {
+				writer.append("c DIMACS written graph by JGAlgo") //
+						.append(System.lineSeparator());
+				final int num_vertices = graph.vertices().size();
+				final int num_edges = graph.edges().size();
+				final Weights.Int w = graph.getEdgesWeights("weightsEdges");
+				final boolean hash_weights = w != null;
+				if (hash_weights)
+					writer.append("p sp " + num_vertices + " " + num_edges) //
+							.append(System.lineSeparator());
+				else
+					writer.append("p edge " + num_vertices + " " + num_edges) //
+							.append(System.lineSeparator());
+
+				// writes all edges, optional with weights
+				for (int e : graph.edges()) {
+					writer.append("e " + graph.edgeSource(e) + " " + graph.edgeTarget(e));
+					if (hash_weights) {
+						int the_weight = w.getInt(e);
+						writer.append(" " + the_weight);
+					}
+					writer.append(System.lineSeparator());
+				}
+
+			} catch (IOException e) {
+				throw new UncheckedIOException(e);
+			}
+
 		}
 
 	}
 
 	private static class ReaderImpl implements GraphReader {
 
+		/**
+		 * Support 2 DIMACS formats:<br>
+		 * The "DIMACS edge format" and "DIMACS sp format"<br>
+		 * <br>
+		 * 1. Basic DIMACS format: <br>
+		 * see https://github.com/akinanop/mvl-solver/wiki/DIMACS-Graph-Format
+		 * 
+		 * <pre>
+		p edge <NumVertices> <NumEdges>
+		e <VertexName1> <VertexName2>
+		Example:
+		c this is the graph with vertices {1,2,3,4,5} and edges {(1,2),(2,3),(2,4),(3,4),(4,5)}
+		p edge 5 5
+		e 1 2
+		e 2 3
+		e 2 4
+		e 3 4
+		e 4 5
+		 * </pre>
+		 * 
+		 * 2. Shortest path format (with weights)<br>
+		 * Two assumptions:<br>
+		 * (1) Undirected graph.<br>
+		 * (2) Weights are integers.<br>
+		 * <br>
+		 * The .gr files:<br>
+		 * see http://www.diag.uniroma1.it/challenge9/format.shtml#graph
+		 * 
+		 * <pre>
+			c
+			p sp n nm
+			a u v w
+		 * </pre>
+		 */
 		@Override
 		public GraphBuilder readIntoBuilder(Reader reader) {
-			// TODO Auto-generated method stub
-			throw new UnsupportedOperationException("Unimplemented method 'readIntoBuilder'");
+			try (BufferedReader br = reader instanceof BufferedReader ? (BufferedReader) reader
+					: new BufferedReader(reader)) {
+				GraphBuilder gb = null;
+				Weights.Int w = null;
+				String line;
+				String graph_format = null;
+				int num_vertices = -1;
+				int num_edges = -1;
+				while ((line = br.readLine()) != null) {
+					// skip empty and comment lines (starts with "c")
+					if (line.trim().length() == 0 || line.trim().startsWith("c"))
+						continue;
+					// replace multiple spaces with just one space
+					line = line.trim().replaceAll("\\s+", " ");
+					if (line.trim().startsWith("p")) {
+						String[] arr = line.split(" ");
+						if (arr.length < 4)
+							throw new IllegalArgumentException(
+									"p lines must have 4 parameters: p edge <NumVertices> <NumEdges> or p sp <NumVertices> <NumEdges>");
+						graph_format = arr[1].toLowerCase();
+						if (!(graph_format.equals("sp") || graph_format.equals("edge")))
+							throw new IllegalArgumentException(
+									"support only: p edge <NumVertices> <NumEdges> or p sp <NumVertices> <NumEdges>");
+						try {
+							num_vertices = Integer.parseInt(arr[2]);
+							num_edges = Integer.parseInt(arr[3]);
+						} catch (Exception e) {
+							throw new IllegalArgumentException(
+									"expect numbers: p edge <NumVertices> <NumEdges> or p sp <NumVertices> <NumEdges>");
+						}
+						if (num_vertices < 1)
+							return gb;
+						gb = GraphBuilder.newUndirected();
+						if (graph_format.equals("sp"))
+							w = gb.addEdgesWeights("weightsEdges", int.class);
+						for (int i = 0; i < num_vertices; i++)
+							gb.addVertex(i + 1); // vertices are labeled as 1,2,3,4...
+						if (num_edges < 1)
+							return gb;
+						continue;
+					}
+
+					// here, we expect edge definition
+					// e source_vertice destination_vertice [weight]
+					if (!line.trim().toLowerCase().startsWith("e"))
+						throw new IllegalArgumentException(
+								"expect edge definition: e <source_vertice> <destination_vertice>");
+					String[] arr = line.split(" ");
+					if (graph_format.equals("sp") && arr.length < 4)
+						throw new IllegalArgumentException(
+								"expect edge definition: e <source_vertice> <destination_vertice> <weight>");
+					if (graph_format.equals("edge") && arr.length < 3)
+						throw new IllegalArgumentException(
+								"expect edge definition: e <source_vertice> <destination_vertice>");
+					int vertice_source = -1;
+					int vertice_target = -1;
+					int edge_weight = -1;
+					try {
+						vertice_source = Integer.parseInt(arr[1]);
+						vertice_target = Integer.parseInt(arr[2]);
+						if (graph_format.equals("sp"))
+							edge_weight = Integer.parseInt(arr[3]);
+					} catch (Exception e) {
+						if (graph_format.equals("sp"))
+							throw new IllegalArgumentException("edge must have 2 vertices as numbers and a weight");
+						throw new IllegalArgumentException("edge must have 2 vertices as numbers");
+					}
+					if (vertice_source < 1 || vertice_source > num_vertices //
+							|| vertice_target < 1 || vertice_target > num_vertices)
+						throw new IllegalArgumentException("vertice nmber must be betwen 1 and num_vertices");
+					// vertices labels 1..num_vertices are mapped to 0..num_vertices-1
+					final int e = gb.addEdge(vertice_source, vertice_target);
+					if (graph_format.equals("sp"))
+						w.set(e, edge_weight);
+					continue;
+				}
+				return gb;
+
+			} catch (IOException e) {
+				throw new UncheckedIOException(e);
+			}
 		}
 
 	}

jgalgo-io/src/test/java/com/jgalgo/io/FormatDIMACSTest.java

@@ -0,0 +1,118 @@
+/*-
+ * Copyright 2023 Barak Ugav
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.jgalgo.io;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import java.io.StringReader;
+import java.io.StringWriter;
+import java.util.Random;
+import org.junit.jupiter.api.Test;
+import com.jgalgo.graph.Graph;
+import com.jgalgo.graph.GraphBuilder;
+import com.jgalgo.graph.GraphFactory;
+import com.jgalgo.graph.Weights;
+
+public class FormatDIMACSTest {
+
+	@Test
+	public void parseDimacsEdgeGraph() {
+		String data = "";
+		data += "c this is the graph with vertices {1,2,3,4,5} and edges {(1,2),(2,3),(2,4),(3,4),(4,5)}\n";
+		data += "p edge 5 5\n";
+		data += "e 1 2\n";
+		data += "e 2 3\n";
+		data += "e 2 4\n";
+		data += "e 3 4\n";
+		data += "e 4 5\n";
+		final Graph g = GraphReader.newInstance("dimacs").readGraph(new StringReader(data));
+
+		final StringWriter writer = new StringWriter();
+		GraphWriter.newInstance("dimacs").writeGraph(g, writer);
+		String data2 = writer.toString();
+
+		String check_data2 = "";
+		check_data2 += "c DIMACS written graph by JGAlgo\n";
+		check_data2 += "p edge 5 5\n";
+		check_data2 += "e 1 2\n";
+		check_data2 += "e 2 3\n";
+		check_data2 += "e 2 4\n";
+		check_data2 += "e 3 4\n";
+		check_data2 += "e 4 5\n";
+		check_data2 = check_data2.replace("\n", System.lineSeparator());
+		String check_data3 = "";
+		check_data3 += "c DIMACS written graph by JGAlgo\n";
+		check_data3 += "p edge 5 5\n";
+		check_data3 += "e 1 2\n";
+		check_data3 += "e 2 4\n";
+		check_data3 += "e 2 3\n";
+		check_data3 += "e 3 4\n";
+		check_data3 += "e 4 5\n";
+		check_data3 = check_data3.replace("\n", System.lineSeparator());
+
+		if (data2.trim().equals(check_data2.trim()))
+			assertEquals(data2.trim(), check_data2.trim());
+		else if (data2.trim().equals(check_data3.trim()))
+			assertEquals(data2.trim(), check_data3.trim());
+		else
+			assertEquals(data2.trim(), check_data2.trim());
+	}
+
+	@Test
+	public void parseDimacsSpGraph() {
+		String data = "";
+		data += "c this is the graph\n";
+		data += "p sp 5 5\n";
+		data += "e 1 2 3\n";
+		data += "e 2 3 9\n";
+		data += "e 2 4 15\n";
+		data += "e 3 4 2\n";
+		data += "e 4 5 7\n";
+		final Graph g = GraphReader.newInstance("dimacs").readGraph(new StringReader(data));
+
+		final StringWriter writer = new StringWriter();
+		GraphWriter.newInstance("dimacs").writeGraph(g, writer);
+		String data2 = writer.toString();
+
+		String check_data2 = "";
+		check_data2 += "c DIMACS written graph by JGAlgo\n";
+		check_data2 += "p sp 5 5\n";
+		check_data2 += "e 1 2 3\n";
+		check_data2 += "e 2 3 9\n";
+		check_data2 += "e 2 4 15\n";
+		check_data2 += "e 3 4 2\n";
+		check_data2 += "e 4 5 7\n";
+		check_data2 = check_data2.replace("\n", System.lineSeparator());
+		String check_data3 = "";
+		check_data3 += "c DIMACS written graph by JGAlgo\n";
+		check_data3 += "p sp 5 5\n";
+		check_data3 += "e 1 2 3\n";
+		check_data3 += "e 2 4 15\n";
+		check_data3 += "e 2 3 9\n";
+		check_data3 += "e 3 4 2\n";
+		check_data3 += "e 4 5 7\n";
+		check_data3 = check_data3.replace("\n", System.lineSeparator());
+
+		if (data2.trim().equals(check_data2.trim()))
+			assertEquals(data2.trim(), check_data2.trim());
+		else if (data2.trim().equals(check_data3.trim()))
+			assertEquals(data2.trim(), check_data3.trim());
+		else
+			assertEquals(data2.trim(), check_data2.trim());
+	}
+
+}