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SCC.java

package gov.nasa.arc.ase.util.graph;

import java.io.IOException;
//#ifdef JDK11



//#else JDK11
import java.util.List;
import java.util.Iterator;
import java.util.LinkedList;
//#endif JDK11

public class SCC {
  private static class SCCState {
    public int N = 0;
    public int SCC = 0;
    public List L = new LinkedList();
  }

  public static void help() {
    System.err.println("usage:");
    System.err.println("\tDegenalize [-join|-degeneralize] [outfile]");
    System.exit(1);
  }  
  public static void main(String[] args) {
    String outname = null;

    for(int i = 0, l = args.length; i < l; i++) {
      if(outname == null)
    outname = args[i];
      else
    help();
    }

    try {
//#ifdef BANDERA
      Graph g = Graph.load(System.getProperty("user.dir")+java.io.File.separator+"out.sm");
//#else BANDERA

//#endif BANDERA

      List scc = scc(g);

      for(Iterator i = scc.iterator(); i.hasNext(); ) {
    List l = (List)i.next();
    System.out.println("component:");
    for(Iterator j = l.iterator(); j.hasNext(); ) {
      Node n = (Node)j.next();

      System.out.println("  " + n.getStringAttribute("label"));
    }
    System.out.println();
      }

      if(outname == null)
    g.save();
      else
//#ifdef BANDERA
        g.save(System.getProperty("user.dir")+java.io.File.separator+outname);
//#else BANDERA

//#endif BANDERA
    } catch(IOException e) {
      e.printStackTrace();
      return;
    }
  }  
  public static void print(List sccs) {
    System.out.println("Strongly connected components:");

    int cnt = 0;
    for(Iterator i = sccs.iterator(); i.hasNext(); ) {
      List scc = (List)i.next();

      System.out.println("\tSCC #" + (cnt++));
      for(Iterator j = scc.iterator(); j.hasNext(); ) {
    Node n = (Node)j.next();
    System.out.println("\t\t" + n.getId() + " - " +
        n.getStringAttribute("label"));
      }
    }
  }  
  public static List scc(Graph g) {
    Node init = g.getInit();
    
    if(init == null) return new LinkedList();

    init.setBooleanAttribute("_reached", true);
    SCCState s = new SCCState();
    visit(init, s);

    final List[] scc = new List[s.SCC];
    for(int i = 0; i < s.SCC; i++)
      scc[i] = new LinkedList();

    g.forAllNodes(new EmptyVisitor() {
      public void visitNode(Node n) {
    scc[n.getIntAttribute("_scc")].add(n);

    n.setBooleanAttribute("_reached", false);
    n.setBooleanAttribute("_dfsnum", false);
    n.setBooleanAttribute("_low", false);
    n.setBooleanAttribute("_scc", false);
      }
    });

    List list = new LinkedList();
    for(int i = 0; i < s.SCC; i++)
      list.add(scc[i]);

    return list;
  }  
  private static void visit(Node p, SCCState s) {
    s.L.add(0, p);
    p.setIntAttribute("_dfsnum", s.N);
    p.setIntAttribute("_low", s.N);
    s.N++;
    for(Iterator i = p.getOutgoingEdges().iterator(); i.hasNext(); ) {
      Edge e = (Edge)i.next();
      Node q = e.getNext();

      if(!q.getBooleanAttribute("_reached")) {
    q.setBooleanAttribute("_reached", true);
    visit(q, s);
    p.setIntAttribute("_low", Math.min(p.getIntAttribute("_low"),
          q.getIntAttribute("_low")));
      } else 
    if(q.getIntAttribute("_dfsnum") < p.getIntAttribute("_dfsnum"))
      if(s.L.contains(q))
        p.setIntAttribute("_low", Math.min(p.getIntAttribute("_low"),
          q.getIntAttribute("_dfsnum")));
    }

    if(p.getIntAttribute("_low") == p.getIntAttribute("_dfsnum")) {
      Node v;
      do {
    v = (Node)s.L.remove(0);
    v.setIntAttribute("_scc", s.SCC);
      } while(v != p);
      s.SCC++;
    }
  }  
}

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