org.hibernate.envers.internal.tools.graph.TopologicalSort Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2013, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.envers.internal.tools.graph;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
/**
* Topological sorting of a graph - based on DFS.
*
* @author Adam Warski (adam at warski dot org)
*/
public class TopologicalSort {
private List sorted;
private int time;
private void process(Vertex v) {
if ( v.getStartTime() != 0 ) {
// alread processed
return;
}
v.setStartTime( time++ );
for ( Vertex n : v.getNeighbours() ) {
process( n );
}
v.setEndTime( time++ );
sorted.add( v.getRepresentation() );
}
public List sort(Collection> vertices) {
sorted = new ArrayList( vertices.size() );
time = 1;
for ( Vertex v : vertices ) {
if ( v.getEndTime() == 0 ) {
process( v );
}
}
Collections.reverse( sorted );
return sorted;
}
}