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-rw-r--r--80-89/86.hs27
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+import Data.Ord (comparing)
+import Data.List (foldl', sortBy)
+
+data Graph a = Graph [a] [(a, a)] deriving (Show, Eq)
+data Adjacency a = Adj [(a, [a])] deriving (Show, Eq)
+
+graphToAdj :: Eq a => Graph a -> Adjacency a
+
+graphToAdj (Graph [] _) = Adj []
+graphToAdj (Graph (v:vs) e) = Adj ((v, e >>= pick):l)
+ where pick (a, b)
+ | a == v = [b]
+ | b == v = [a]
+ | otherwise = []
+ Adj l = graphToAdj $ Graph vs e
+
+kColor :: Eq a => Graph a -> [(a, Int)]
+
+takeUntil _ [] = []
+takeUntil p (x:xs) = x:if p x then [] else takeUntil p xs
+
+kColor g = last $ takeUntil (\c' -> length c' == length vs') $ scanl (\c' x -> round c' x) [] [1..]
+ where (Adj vs) = graphToAdj g
+ vs' = sortBy (comparing (length . snd)) vs
+ getc c u = filter ((== u) . fst) c
+ ok c l cur = all (/= cur) [snd $ head col | v <- l, let col = getc c v, col /= []]
+ round c cur = foldl' (\c' (u, adj) -> if (getc c' u == []) && ok c' adj cur then (u, cur):c' else c') c vs'