Пример #1
0
  /**
   * Algorithm of Tarjan for computing the strongly connected components of a graph.
   *
   * @param v current node
   * @throws QueryException if a variable directly calls itself
   */
  private void tarjan(final int v) throws QueryException {
    final int ixv = 2 * v, llv = ixv + 1, idx = next++;
    while (list.size() <= llv) list.add(-1);
    list.set(ixv, idx);
    list.set(llv, idx);

    stack.push(v);

    for (final int w : adjacentTo(v)) {
      final int ixw = 2 * w, llw = ixw + 1;
      if (list.size() <= ixw || list.get(ixw) < 0) {
        // Successor w has not yet been visited; recurse on it
        tarjan(w);
        list.set(llv, Math.min(list.get(llv), list.get(llw)));
      } else if (stack.contains(w)) {
        // Successor w is in stack S and hence in the current SCC
        list.set(llv, Math.min(list.get(llv), list.get(ixw)));
      }
    }

    // If v is a root node, pop the stack and generate an SCC
    if (list.get(llv) == list.get(ixv)) {
      int w;
      Scope[] out = null;
      do {
        w = stack.pop();
        final Scope scp = scopes.get(w);
        out = out == null ? new Scope[] {scp} : Array.add(out, scp);
      } while (w != v);
      result.add(out);
    }
  }