Simplifies solve
parent
0f6c8f99bf
commit
37a9684fe1
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@ -1,6 +1,6 @@
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module Main where
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module Main where
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import qualified Control.Applicative
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import Control.Applicative ((<|>))
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import qualified Control.Monad
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import qualified Control.Monad
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import qualified Data.Char
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import qualified Data.Char
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import qualified Data.Function
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import qualified Data.Function
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@ -64,54 +64,60 @@ pruneGrid = fixM pruneGrid'
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where
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where
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fixM f x = f x >>= \x' -> if x' == x then return x else fixM f x'
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fixM f x = f x >>= \x' -> if x' == x then return x else fixM f x'
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isFinishedGrid :: Grid -> Bool
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isFinishedGrid grid = null [ () | Possible _ <- concat grid ]
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isInvalidGrid :: Grid -> Bool
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isInvalidGrid :: Grid -> Bool
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isInvalidGrid grid =
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isInvalidGrid grid =
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any isInvalidRow grid
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any isInvalidRow grid
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|| any isInvalidRow (Data.List.transpose grid)
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|| any isInvalidRow (Data.List.transpose grid)
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|| any isInvalidRow (subGridsToRows grid)
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|| any isInvalidRow (subGridsToRows grid)
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where
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where
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isInvalidRow = not . isValidRow
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isInvalidRow row =
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isValidRow row =
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let fixeds = [x | Fixed x <- row]
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let fixeds = [x | Fixed x <- row]
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emptyPossibles = [x | Possible x <- row, null x]
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emptyPossibles = [x | Possible x <- row, null x]
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in length fixeds == length (Data.List.nub fixeds) && null emptyPossibles
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in hasDups fixeds || not (null emptyPossibles)
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isFinishedGrid :: Grid -> Bool
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hasDups l = hasDups' l []
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isFinishedGrid grid = null [ () | Possible _ <- concat grid ]
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hasDups' [] _ = False
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hasDups' (y:ys) xs
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| y `elem` xs = True
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| otherwise = hasDups' ys (y:xs)
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solve :: Grid -> Maybe Grid
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solve :: Grid -> Maybe Grid
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solve grid
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solve grid = pruneGrid grid >>= solve'
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| isInvalidGrid grid = Nothing
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where
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| isFinishedGrid grid = Just grid
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solve' grid
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| otherwise =
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| isInvalidGrid grid = Nothing
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let (grid1, grid2) = splitGrid
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| isFinishedGrid grid = Just grid
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in case pruneGrid grid1 of
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| otherwise =
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Nothing -> pruneGrid grid2 >>= solve
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let (grid1, grid2) = nextGrids grid
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Just grid' -> solve grid' Control.Applicative.<|> (pruneGrid grid2 >>= solve)
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in solve grid1 <|> solve grid2
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where
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possibleVals (Fixed x) = [x]
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possibleVals (Possible xs) = xs
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smallestPossible =
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nextGrids grid =
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Data.List.minimumBy (compare `Data.Function.on` (length . possibleVals . snd))
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let (i, first@(Fixed _), rest) = splitPossible . smallestPossible $ grid
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[(i, c) | (i, c@(Possible _)) <- zip [0..] $ concat grid]
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in (replace2D i first grid, replace2D i rest grid)
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splitPossible (i, Possible (x:[y])) = (i, Fixed x, Fixed y)
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smallestPossible grid =
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splitPossible (i, Possible (x:xs)) = (i, Fixed x, Possible xs)
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Data.List.minimumBy (compare `Data.Function.on` (length . possibleVals . snd))
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splitPossible _ = error "Impossible case"
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[(i, c) | (i, c@(Possible _)) <- zip [0..] $ concat grid]
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splitGrid =
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possibleVals (Fixed x) = [x]
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let (i, first@(Fixed _), rest) = splitPossible smallestPossible
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possibleVals (Possible xs) = xs
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in (replace2D i first grid, replace2D i rest grid)
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replace2D i v = let (x, y) = (i `quot` 9, i `mod` 9) in replace x (replace y (const v))
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splitPossible (i, Possible (x:[y])) = (i, Fixed x, Fixed y)
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replace p f xs = [if i == p then f x else x | (x, i) <- zip xs [0..]]
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splitPossible (i, Possible (x:xs)) = (i, Fixed x, Possible xs)
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splitPossible _ = error "Impossible case"
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replace2D i v = let (x, y) = (i `quot` 9, i `mod` 9) in replace x (replace y (const v))
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replace p f xs = [if i == p then f x else x | (x, i) <- zip xs [0..]]
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main = do
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main = do
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grids <- lines <$> getContents
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grids <- lines <$> getContents
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Control.Monad.forM_ grids $ \grid ->
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Control.Monad.forM_ grids $ \grid ->
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case readGrid grid of
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case readGrid grid of
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Nothing -> putStrLn "Invalid grid"
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Nothing -> putStrLn "Invalid grid"
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Just grid -> case pruneGrid grid >>= solve of
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Just grid -> case solve grid of
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Nothing -> putStrLn "No solution found"
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Nothing -> putStrLn "No solution found"
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Just grid' -> putStrLn $ showGrid grid'
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Just grid' -> putStrLn $ showGrid grid'
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