add articulation points and bridges

src/IGraph/Algorithms/Structure.chs

@@ -12,6 +12,9 @@ module IGraph.Algorithms.Structure
     , isConnected
     , isStronglyConnected
     , decompose
+    , articulationPoints
+    , bridges
+      -- * Topological Sorting, Directed Acyclic Graphs
     , isDag
     , topSort
     , topSortUnsafe
@@ -192,6 +195,27 @@ decompose gr = unsafePerformIO $ allocaVectorPtr $ \ptr -> do
     , `Int'
     } -> `CInt' void- #}
 
+-- | Find the articulation points in a graph.
+articulationPoints :: Graph d v e -> [Node]
+articulationPoints gr = unsafePerformIO $ allocaVector $ \res -> do
+  igraphArticulationPoints (_graph gr) res
+  toNodes res
+{-#INLINE igraphArticulationPoints #-}
+{#fun igraph_articulation_points as ^
+    { `IGraph'
+    , castPtr `Ptr Vector'
+    } -> `CInt' void- #}
+
+-- ^ Find all bridges in a graph.
+bridges :: Graph d v e -> [Edge]
+bridges gr = unsafePerformIO $ allocaVector $ \res -> do
+  igraphBridges (_graph gr) res
+  map (getEdgeByEid gr) <$> toNodes res
+{-# INLINE igraphBridges #-}
+{#fun igraph_bridges as ^
+    { `IGraph'
+    , castPtr `Ptr Vector'
+    } -> `CInt' void- #}
 
 -- | Checks whether a graph is a directed acyclic graph (DAG) or not.
 isDag :: Graph d v e -> Bool

tests/Test/Algorithms.hs

@@ -27,6 +27,8 @@ tests = testGroup "Algorithms"
     , radiusTest
     , subGraphs
     , decomposeTest
+    , articulationTest
+    , bridgeTest
     , pagerankTest
     , kleinbergTest
     ]
@@ -124,6 +126,18 @@ decomposeTest = testGroup "Decompose"
 		 , (8,9), (9,10) ]
     gr = mkGraph (replicate 11 ()) $ zip es $ repeat () :: Graph 'U () ()
 
+articulationTest :: TestTree
+articulationTest = testCase "Articulation points" $
+  articulationPoints (star 3) @?= [0]
+
+bridgeTest :: TestTree
+bridgeTest = testCase "Bridges" $ edgeLab g <$> bridges g @?= ["bridge"]
+  where g = fromLabeledEdges @'U
+            [ (("a","b"),"ab") , (("b","c"),"bc") , (("c","a"),"ca")
+            , (("i","j"),"ij") , (("j","k"),"jk") , (("k","i"),"ki")
+            , (("a","i"),"bridge")
+            ]
+
 {-
 communityTest :: TestTree
 communityTest = testGroup "Community"