29 lines
867 B
Haskell
29 lines
867 B
Haskell
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module Day5 (BoardingPass(BoardingPass), seatId) where
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data BoardingPass = BoardingPass { row :: Int, column :: Int }
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deriving (Show)
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binaryStringToInt b = binaryStringToInt' (reverse b) 0 0
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where
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binaryStringToInt' [] _ acc = acc
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binaryStringToInt' ('1':bs) m acc = binaryStringToInt' bs (m+1) (acc + 2^m)
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binaryStringToInt' ('0':bs) m acc = binaryStringToInt' bs (m+1) acc
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charToBinaryDigit 'F' = '0'
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charToBinaryDigit 'L' = '0'
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charToBinaryDigit 'B' = '1'
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charToBinaryDigit 'R' = '1'
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stringToInt = binaryStringToInt . map charToBinaryDigit
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readBoardingPass str =
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let (str', rest) = splitAt 10 str
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(rowS, colS) = splitAt 7 str'
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in
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(BoardingPass (stringToInt rowS) (stringToInt colS), rest)
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instance Read BoardingPass where
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readsPrec _ str = [readBoardingPass str]
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seatId (BoardingPass row column) = row * 8 + column
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