Changes in / [984:a337a0dd3f75:993:ad40f7d32846] in lemon-1.2

Files:

• lemon/connectivity.h (modified) (1 diff)
• test/connectivity_test.cc (modified) (1 diff)

lemon/connectivity.h

@@ -746 +746 @@
   ///
   /// This function checks whether the given undirected graph is
-  /// bi-node-connected, i.e. any two edges are on same circle.
+  /// bi-node-connected, i.e. a connected graph without articulation
+  /// node.
   ///
   /// \return \c true if the graph bi-node-connected.
-  /// \note By definition, the empty graph is bi-node-connected.
+  ///
+  /// \note By definition,
+  /// \li a graph consisting of zero or one node is bi-node-connected,
+  /// \li a graph consisting of two isolated nodes
+  /// is \e not bi-node-connected and
+  /// \li a graph consisting of two nodes connected by an edge
+  /// is bi-node-connected.
   ///
   /// \see countBiNodeConnectedComponents(), biNodeConnectedComponents()
   template <typename Graph>
   bool biNodeConnected(const Graph& graph) {
+    bool hasNonIsolated = false, hasIsolated = false;
+    for (typename Graph::NodeIt n(graph); n != INVALID; ++n) {
+      if (typename Graph::OutArcIt(graph, n) == INVALID) {
+        if (hasIsolated || hasNonIsolated) {
+          return false;
+        } else {
+          hasIsolated = true;
+        }
+      } else {
+        if (hasIsolated) {
+          return false;
+        } else {
+          hasNonIsolated = true;
+        }
+      }
+    }
     return countBiNodeConnectedComponents(graph) <= 1;
   }

test/connectivity_test.cc

@@ -98 +98 @@
     check(simpleGraph(g), "This graph is simple.");
   }
+
+  {
+    ListGraph g;
+    ListGraph::NodeMap<bool> map(g);
+
+    ListGraph::Node n1 = g.addNode();
+    ListGraph::Node n2 = g.addNode();
+
+    ListGraph::Edge e1 = g.addEdge(n1, n2);
+    ::lemon::ignore_unused_variable_warning(e1);
+    check(biNodeConnected(g), "Graph is bi-node-connected");
+
+    ListGraph::Node n3 = g.addNode();
+    ::lemon::ignore_unused_variable_warning(n3);
+    check(!biNodeConnected(g), "Graph is not bi-node-connected");
+  }
+
 
   {