package algo.graph;
import ds.graph.Graph;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* Created by sherxon on 1/4/17.
*/
public class TopologicalSorting extends DFS {
List<Integer> list;
public TopologicalSorting(Graph graph) {
super(graph);
list = new ArrayList<>();
}
// this works with DAG Only
// first we will choose any vertex who that does not have incoming edges (sources)
// sources can be found easier if incoming edge count is recorded in each vertex
List<Integer> topSort() {
Set<Integer> sources = new HashSet<>();
for (Integer vertex : graph.getVertices())
sources.add(vertex);
for (Integer vertex : graph.getVertices())
for (Integer tVertex : graph.getNeighbors(vertex))
sources.remove(tVertex);
for (Integer source : sources)
if (!visited.contains(source))
search(source);
return list;
}
@Override
public void processVertex(Integer source) {
super.processVertex(source);
list.add(source);
}
}