org.jgrapht.generate.WindmillGraphsGenerator Maven / Gradle / Ivy
/*
* (C) Copyright 2017-2023, by Joris Kinable 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.*;
/**
* Generator for Windmill Graphs,
* Dutch Windmill Graphs and
* Friendship Graphs.
*
* The windmill graph $W_n^{(m)}$ is the graph obtained by taking $m$ copies of the complete graph
* $K_n$ with a vertex in common. The Dutch windmill graph $D_n^{(m)}$, is the graph obtained by
* taking $m$ copies of the cycle graph $C_3$ with a vertex in common. For the special case where
* $n=3$, $D_n^{(m)}$ and $W_n^{(m)}$ are identical. The class of graphs $D_3^{(m)}$ is sometimes
* referred to as the Friendship graph, denoted by $F_m$.
*
* @author Joris Kinable
*
* @param graph vertex type
* @param graph edge type
*/
public class WindmillGraphsGenerator
implements GraphGenerator
{
/**
* WINDMILL and DUTCHWINDMILL Modes for the Constructor
*/
public enum Mode
{
WINDMILL,
DUTCHWINDMILL
}
private final Mode mode;
private final int m;
private final int n;
/**
* Constructs a GeneralizedPetersenGraphGenerator used to generate a Generalized Petersen graphs
* $GP(n,k)$.
*
* @param mode indicate whether the generator should generate Windmill graphs or Dutch Windmill
* graphs
* @param m number of copies of $C_n$ (Dutch Windmill graph) or $K_n$ (Windmill graph)
* @param n size of $C_n$ (Dutch Windmill graph) or $K_n$ (Windmill graph). To generate
* friendship graphs, set $n=3$ (the mode is irrelevant).
*/
public WindmillGraphsGenerator(Mode mode, int m, int n)
{
if (m < 2)
throw new IllegalArgumentException("m must be larger or equal than 2");
if (n < 3)
throw new IllegalArgumentException("n must be larger or equal than 3");
this.mode = mode;
this.m = m;
this.n = n;
}
@Override
public void generateGraph(Graph target, Map resultMap)
{
V center = target.addVertex();
List sub = new ArrayList<>(n);
if (mode == Mode.DUTCHWINDMILL) { // Generate Dutch windmill graph
for (int i = 0; i < m; i++) { // m copies of cycle graph Cn
sub.clear();
sub.add(center);
for (int j = 1; j < n; j++) {
sub.add(target.addVertex());
}
for (int r = 0; r < sub.size(); r++)
target.addEdge(sub.get(r), sub.get((r + 1) % n));
}
} else { // Generate windmill graph
for (int i = 0; i < m; i++) { // m copies of complete graph Kn
sub.clear();
sub.add(center);
for (int j = 1; j < n; j++) {
sub.add(target.addVertex());
}
for (int r = 0; r < sub.size() - 1; r++)
for (int s = r + 1; s < sub.size(); s++)
target.addEdge(sub.get(r), sub.get(s));
}
}
}
}