qilin.util.graph.TopologicalSorter Maven / Gradle / Ivy

Go to download
/* Qilin - a Java Pointer Analysis Framework
 * Copyright (C) 2021-2030 Qilin developers
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3.0 of the
 * License, or (at your option) any later version.
 *
 * 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 General Lesser Public License for more details.
 *
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 */

package qilin.util.graph;

import java.util.*;

public class TopologicalSorter {
  private DirectedGraph graph;
  private List sortedList;
  private Set visited;

  public List sort(final DirectedGraph graph) {
    return this.sort(graph, false);
  }

  public List sort(final DirectedGraph graph, final boolean reverse) {
    this.initialize(graph);
    graph.allNodes().stream().filter(n -> graph.succsOf(n).isEmpty()).forEach(this::visit);
    List result = this.sortedList;
    if (reverse) {
      Collections.reverse(result);
    }
    this.clear();
    return result;
  }

  private void initialize(final DirectedGraph graph) {
    this.graph = graph;
    this.sortedList = new LinkedList<>();
    this.visited = new HashSet<>();
  }

  private void visit(final N node) {
    if (!this.visited.contains(node)) {
      this.visited.add(node);
      this.graph.predsOf(node).forEach(this::visit);
      this.sortedList.add(node);
    }
  }

  private void clear() {
    this.graph = null;
    this.sortedList = null;
    this.visited = null;
  }
}