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  1. import Control.Monad
  2.  
  3. import Data.Array
  4.  
  5. yoba rangeArr end start = minimumOp [arr ! (end, x) | x <- [0 .. sizeX]]
  6.  
  7.   where bounds' @ ((0, 0), (sizeY, sizeX)) = bounds rangeArr
  8.  
  9.         arr = listArray bounds' [value y x | y <- [0 .. sizeY], x <- [0 .. sizeX]]
  10.  
  11.         value y _ | y == start = Just 0
  12.         value _ 0              = Nothing
  13.         value y x              = minimumOp [(arr ! (n, x - 1)) `addOp` (rangeArr ! (n, y)) | n <- [0 .. sizeY]]
  14.  
  15.         addOp = liftM2 (+)
  16.  
  17.         minimumOp = foldl minOp Nothing
  18.  
  19.           where Just v1 `minOp` Just v2 = Just $ min v1 v2
  20.                 Just v1 `minOp` Nothing = Just v1
  21.                 Nothing `minOp` Just v2 = Just v2
  22.                 Nothing `minOp` Nothing = Nothing        
  23.  
  24.  
  25. main = print $ yoba (toArray2D graph) end start
  26.  
  27.   where end   = 4
  28.         start = 0
  29.  
  30.         graph = [[Nothing, Just  7, Just  9, Nothing, Nothing, Just 14],
  31.                  [Just  7, Nothing, Just 10, Just 15, Nothing, Nothing],
  32.                  [Just  9, Just 10, Nothing, Just 11, Nothing, Just  2],
  33.                  [Nothing, Just 15, Just 11, Nothing, Just  6, Nothing],
  34.                  [Nothing, Nothing, Nothing, Just  6, Nothing, Just  9],
  35.                  [Just 14, Nothing, Just  2, Nothing, Just  9, Nothing]]
  36.  
  37.         toArray2D source = listArray ((0, 0), (size, size)) [source !! y !! x | y <- [0 .. size], x <- [0 .. size]]
  38.  
  39.           where size = length source - 1
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Standard input is empty
compilation info 
[1 of 1] Compiling Main             ( prog.hs, prog.o )
Linking prog ...
stdout
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Just 20
https://ideone.com/VtnCi
language:
Haskell (ghc 8.4.4)
created:
12 years ago
visibility:
public

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