-- (c) 2000-2005 by Martin Erwig [see file COPYRIGHT] -- | Minimum-Spanning-Tree Algorithms module Data.Graph.Inductive.Query.MST ( msTreeAt,msTree, -- * Path in MST msPath, -- * Types used LRTree ) where import Data.Graph.Inductive.Graph import qualified Data.Graph.Inductive.Internal.Heap as H import Data.Graph.Inductive.Internal.RootPath newEdges :: LPath b -> Context a b -> [H.Heap b (LPath b)] newEdges (LP p) (_,_,_,s) = map (\(l,v)->H.unit l (LP ((v,l):p))) s prim :: (Graph gr,Real b) => H.Heap b (LPath b) -> gr a b -> LRTree b prim h g | H.isEmpty h || isEmpty g = [] prim h g = case match v g of (Just c,g') -> p:prim (H.mergeAll (h':newEdges p c)) g' (Nothing,g') -> prim h' g' where (_,p@(LP ((v,_):_)),h') = H.splitMin h msTreeAt :: (Graph gr,Real b) => Node -> gr a b -> LRTree b msTreeAt v = prim (H.unit 0 (LP [(v,0)])) msTree :: (Graph gr,Real b) => gr a b -> LRTree b msTree g = msTreeAt v g where ((_,v,_,_),_) = matchAny g msPath :: LRTree b -> Node -> Node -> Path msPath t a b = joinPaths (getLPathNodes a t) (getLPathNodes b t) joinPaths :: Path -> Path -> Path joinPaths p = joinAt (head p) p joinAt :: Node -> Path -> Path -> Path joinAt _ (v:vs) (w:ws) | v==w = joinAt v vs ws joinAt x p q = reverse p++(x:q)