COIN-OR::LEMON - Graph Library

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  • lemon/connectivity.h

    r956 r1268  
    746746  ///
    747747  /// This function checks whether the given undirected graph is
    748   /// bi-node-connected, i.e. any two edges are on same circle.
     748  /// bi-node-connected, i.e. a connected graph without articulation
     749  /// node.
    749750  ///
    750751  /// \return \c true if the graph bi-node-connected.
    751   /// \note By definition, the empty graph is bi-node-connected.
     752  ///
     753  /// \note By definition,
     754  /// \li a graph consisting of zero or one node is bi-node-connected,
     755  /// \li a graph consisting of two isolated nodes
     756  /// is \e not bi-node-connected and
     757  /// \li a graph consisting of two nodes connected by an edge
     758  /// is bi-node-connected.
    752759  ///
    753760  /// \see countBiNodeConnectedComponents(), biNodeConnectedComponents()
    754761  template <typename Graph>
    755762  bool biNodeConnected(const Graph& graph) {
     763    bool hasNonIsolated = false, hasIsolated = false;
     764    for (typename Graph::NodeIt n(graph); n != INVALID; ++n) {
     765      if (typename Graph::OutArcIt(graph, n) == INVALID) {
     766        if (hasIsolated || hasNonIsolated) {
     767          return false;
     768        } else {
     769          hasIsolated = true;
     770        }
     771      } else {
     772        if (hasIsolated) {
     773          return false;
     774        } else {
     775          hasNonIsolated = true;
     776        }
     777      }
     778    }
    756779    return countBiNodeConnectedComponents(graph) <= 1;
    757780  }
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