diGraph.cpp

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 *   Copyright (c) 2005-2025 by                                             *
 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
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 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
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#include <agrum/base/graphs/diGraph.h>
#include <agrum/base/graphs/graphElements.h>
 
#ifdef GUM_NO_INLINE
#  include <agrum/base/graphs/diGraph_inl.h>
#endif   // GUM_NO_INLINE
 
namespace gum {
 
  DiGraph DiGraph::completeGraph(int n) {
    DiGraph g;
    g.addNodes(n);
 
    for (int j = 0; j < n; ++j) {
      for (int k = j + 1; k < n; ++k) {
        g.addArc(j, k);
      }
    }
    return g;
  }
 
  DiGraph::DiGraph(Size nodes_size,
                   bool nodes_resize_policy,
                   Size arcs_size,
                   bool arcs_resize_policy) :
      NodeGraphPart(nodes_size, nodes_resize_policy), ArcGraphPart(arcs_size, arcs_resize_policy) {
    GUM_CONSTRUCTOR(DiGraph)
  }
 
  DiGraph::DiGraph(const DiGraph& g) : NodeGraphPart(g), ArcGraphPart(g) { GUM_CONS_CPY(DiGraph) }
 
  DiGraph::~DiGraph() { GUM_DESTRUCTOR(DiGraph) }
 
  std::string DiGraph::toString() const {
    std::string s = NodeGraphPart::toString();
    s += " , ";
    s += ArcGraphPart::toString();
    return s;
  }
 
  std::string DiGraph::toDot() const {
    std::stringstream strBuff;
    std::string       tab = "     ";
    strBuff << "digraph {" << std::endl;
 
    for (const auto node: nodes())
      strBuff << tab << node << ";" << std::endl;
 
    strBuff << std::endl;
 
    for (const auto& arc: arcs())
      strBuff << tab << arc.tail() << " -> " << arc.head() << ";" << std::endl;
 
    strBuff << "}" << std::endl << std::endl;
    return strBuff.str();
  }

  std::ostream& operator<<(std::ostream& stream, const DiGraph& g) {
    stream << g.toString();
    return stream;
  }
 
  Sequence< NodeId > DiGraph::topologicalOrder() const {
    Sequence< NodeId > topologicalOrder;
    const auto&        dag = *this;
 
    if (dag.empty()) return topologicalOrder;
 
    auto border = std::vector< NodeId >();
    border.reserve(dag.size() / 2);
    auto count = dag.nodesPropertyFromVal< Size >(0, dag.size());
    for (const auto node: dag.nodes()) {
      if (dag.parents(node).empty()) { border.push_back(node); }
      count[node] = dag.parents(node).size();
    }
 
    if (border.empty()) {
      GUM_ERROR(InvalidDirectedCycle, "cycles prevent the creation of a topological ordering.");
    }
 
    while (!border.empty()) {
      const auto root = border.back();
      border.pop_back();
 
      if (topologicalOrder.exists(root)) {
        GUM_ERROR(InvalidDirectedCycle, "cycles prevent the creation of a topological ordering.");
      }
      topologicalOrder.insert(root);
 
      for (const auto child: dag.children(root)) {
        if (count[child] == 1) { border.push_back(child); }
        if (count[child] == 0) {
          GUM_ERROR(InvalidDirectedCycle, "cycles prevent the creation of a topological ordering.");
        }
        count[child]--;
      }
    }
 
    GUM_ASSERT(topologicalOrder.size() == dag.size());
    return topologicalOrder;
  }
 
  bool DiGraph::hasDirectedPath(const NodeId from, const NodeId to) {
    if (!exists(from)) return false;
 
    // not recursive version => use a FIFO for simulating the recursion
    List< NodeId > nodeFIFO;
    nodeFIFO.pushBack(from);
 
    NodeSet marked;
    marked.insert(from);
 
    NodeId new_one;
 
    while (!nodeFIFO.empty()) {
      new_one = nodeFIFO.front();
      nodeFIFO.popFront();
 
      for (const auto chi: children(new_one)) {
        if (chi == to) return true;
 
        if (!marked.contains(chi)) {
          nodeFIFO.pushBack(chi);
          marked.insert(chi);
        }
      }
    }
 
    return false;
  }
 
} /* namespace gum */