1.1 --- a/lemon/connectivity.h	Wed Aug 07 06:31:47 2013 +0200
     1.2 +++ b/lemon/connectivity.h	Fri Aug 09 14:01:24 2013 +0200
     1.3 @@ -745,14 +745,37 @@
     1.4    /// \brief Check whether an undirected graph is bi-node-connected.
     1.5    ///
     1.6    /// This function checks whether the given undirected graph is
     1.7 -  /// bi-node-connected, i.e. any two edges are on same circle.
     1.8 +  /// bi-node-connected, i.e. a connected graph without articulation
     1.9 +  /// node.
    1.10    ///
    1.11    /// \return \c true if the graph bi-node-connected.
    1.12 -  /// \note By definition, the empty graph is bi-node-connected.
    1.13 +  ///
    1.14 +  /// \note By definition,
    1.15 +  /// \li a graph consisting of zero or one node is bi-node-connected,
    1.16 +  /// \li a graph consisting of two isolated nodes
    1.17 +  /// is \e not bi-node-connected and
    1.18 +  /// \li a graph consisting of two nodes connected by an edge
    1.19 +  /// is bi-node-connected.
    1.20    ///
    1.21    /// \see countBiNodeConnectedComponents(), biNodeConnectedComponents()
    1.22    template <typename Graph>
    1.23    bool biNodeConnected(const Graph& graph) {
    1.24 +    bool hasNonIsolated = false, hasIsolated = false;
    1.25 +    for (typename Graph::NodeIt n(graph); n != INVALID; ++n) {
    1.26 +      if (typename Graph::OutArcIt(graph, n) == INVALID) {
    1.27 +        if (hasIsolated || hasNonIsolated) {
    1.28 +          return false;
    1.29 +        } else {
    1.30 +          hasIsolated = true;
    1.31 +        }
    1.32 +      } else {
    1.33 +        if (hasIsolated) {
    1.34 +          return false;
    1.35 +        } else {
    1.36 +          hasNonIsolated = true;
    1.37 +        }
    1.38 +      }
    1.39 +    }
    1.40      return countBiNodeConnectedComponents(graph) <= 1;
    1.41    }
    1.42  

     2.1 --- a/test/connectivity_test.cc	Wed Aug 07 06:31:47 2013 +0200
     2.2 +++ b/test/connectivity_test.cc	Fri Aug 09 14:01:24 2013 +0200
     2.3 @@ -99,6 +99,23 @@
     2.4    }
     2.5  
     2.6    {
     2.7 +    ListGraph g;
     2.8 +    ListGraph::NodeMap<bool> map(g);
     2.9 +
    2.10 +    ListGraph::Node n1 = g.addNode();
    2.11 +    ListGraph::Node n2 = g.addNode();
    2.12 +
    2.13 +    ListGraph::Edge e1 = g.addEdge(n1, n2);
    2.14 +    ::lemon::ignore_unused_variable_warning(e1);
    2.15 +    check(biNodeConnected(g), "Graph is bi-node-connected");
    2.16 +
    2.17 +    ListGraph::Node n3 = g.addNode();
    2.18 +    ::lemon::ignore_unused_variable_warning(n3);
    2.19 +    check(!biNodeConnected(g), "Graph is not bi-node-connected");
    2.20 +  }
    2.21 +
    2.22 +
    2.23 +  {
    2.24      Digraph d;
    2.25      Digraph::NodeMap<int> order(d);
    2.26      Graph g(d);