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  1. import Data.List
  2. --import Data.List.Split (chunksOf)
  3.  
  4. solve field | elem '-' field = filter (not.null) $ concatMap solve $ nextstep field
  5.             | otherwise      = [field]
  6.  
  7. nextstep field | m == 0      = [[]]
  8.                | otherwise   = map (\c -> take i field ++ c : drop (i+1) field) v
  9.     where
  10.         freecells = elemIndices '-' field
  11.         (m, i, v) = minimum $ map (\i -> let v = variants i in (length v,i,v)) freecells
  12.  
  13.         variants i  = "123456789" \\ (rownums ++ colnums ++ squnums) where
  14.             (r,c)   = divMod i 9
  15.             rownums = take 9 . drop (r*9) $ field
  16.             colnums = map ((field!!).(+c)) [0,9..80]
  17.             [r',c'] = map (\x -> x `div` 3 * 3) [r,c]
  18.             squnums = concatMap (take 3 . flip drop field . (\x -> (x+r')*9+c')) [0..2]
  19.  
  20. showres fields | null fields = "No solution"
  21. --               | otherwise   = (' ':).intersperse ' '.unlines.chunksOf 9.head $ fields
  22.                | otherwise   = head fields
  23.  
  24. main = do
  25.     let f = "--7---34-\
  26.             \2---38---\
  27.             \1--4----2\
  28.             \-2-9-64--\
  29.             \-7--4--8-\
  30.             \--58-2-1-\
  31.             \8----4--1\
  32.             \---65---9\
  33.             \-32---7--"
  34.     putStr $ showres $ solve f
Success #stdin #stdout 0.01s 4556KB
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597261348246538197183497562328916475971345286465872913859724631714653829632189754
https://ideone.com/LNAMv2
language:
Haskell (ghc 8.4.4)
created:
11 years ago
visibility:
public

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