org.jgrapht.generate.LinearGraphGenerator Maven / Gradle / Ivy
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/*
* (C) Copyright 2003-2023, by John V Sichi and Contributors.
*
* JGraphT : a free Java graph-theory library
*
* See the CONTRIBUTORS.md file distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0, or the
* GNU Lesser General Public License v2.1 or later
* which is available at
* http://www.gnu.org/licenses/old-licenses/lgpl-2.1-standalone.html.
*
* SPDX-License-Identifier: EPL-2.0 OR LGPL-2.1-or-later
*/
package org.jgrapht.generate;
import org.jgrapht.*;
import java.util.*;
/**
* Generates a linear graph of any size. For a directed graph, the edges are oriented from
* START_VERTEX to END_VERTEX.
*
* @param the graph vertex type
* @param the graph edge type
*
* @author John V. Sichi
*/
public class LinearGraphGenerator
implements GraphGenerator
{
/**
* Role for the first vertex generated.
*/
public static final String START_VERTEX = "Start Vertex";
/**
* Role for the last vertex generated.
*/
public static final String END_VERTEX = "End Vertex";
private int size;
/**
* Construct a new LinearGraphGenerator.
*
* @param size number of vertices to be generated
*
* @throws IllegalArgumentException if the specified size is negative.
*/
public LinearGraphGenerator(int size)
{
if (size < 0) {
throw new IllegalArgumentException("must be non-negative");
}
this.size = size;
}
/**
* {@inheritDoc}
*/
@Override
public void generateGraph(Graph target, Map resultMap)
{
V lastVertex = null;
for (int i = 0; i < size; ++i) {
V newVertex = target.addVertex();
if (lastVertex == null) {
if (resultMap != null) {
resultMap.put(START_VERTEX, newVertex);
}
} else {
target.addEdge(lastVertex, newVertex);
}
lastVertex = newVertex;
}
if ((resultMap != null) && (lastVertex != null)) {
resultMap.put(END_VERTEX, lastVertex);
}
}
}