org.hibernate.envers.internal.tools.graph.GraphTopologicalSort Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* License: GNU Lesser General Public License (LGPL), version 2.1 or later.
* See the lgpl.txt file in the root directory or .
*/
package org.hibernate.envers.internal.tools.graph;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* @author Adam Warski (adam at warski dot org)
*/
public final class GraphTopologicalSort {
private GraphTopologicalSort() {
}
/**
* Sorts a graph topologically.
*
* @param definer Defines a graph (values and representations) to sort.
*
* @return Values of the graph, sorted topologically.
*/
public static List sort(GraphDefiner definer) {
final List values = definer.getValues();
final Map> vertices = new HashMap<>();
// Creating a vertex for each representation
for ( V v : values ) {
final R rep = definer.getRepresentation( v );
vertices.put( rep, new Vertex<>( rep ) );
}
// Connecting neighbourhooding vertices
for ( V v : values ) {
for ( V vn : definer.getNeighbours( v ) ) {
vertices.get( definer.getRepresentation( v ) )
.addNeighbour( vertices.get( definer.getRepresentation( vn ) ) );
}
}
// Sorting the representations
final List sortedReps = new TopologicalSort().sort( vertices.values() );
// Transforming the sorted representations to sorted values
final List sortedValues = new ArrayList<>( sortedReps.size() );
for ( R rep : sortedReps ) {
sortedValues.add( definer.getValue( rep ) );
}
return sortedValues;
}
}