Day 03

day03/Commons.hs

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+module Commons where
+
+import GHC.IO.Handle (isEOF)
+import Data.Char (isDigit)
+
+
+data Coordinates = Coordinates { x :: Int, y :: Int } deriving (Eq, Show)
+data NumberPart = NumberPart { value :: Int, numberLength :: Int, neighbors :: [Coordinates] } deriving Show
+data SymbolPart = SymbolPart { symbol :: Char, coordinates :: Coordinates } deriving Show
+data Engine = Engine { numbers :: [NumberPart], symbols :: [SymbolPart] } deriving Show
+
+
+parseNumberPartNeighborsIn :: Int -> Int -> Int -> [Coordinates]
+parseNumberPartNeighborsIn row column length | length > 0 = Coordinates {x = column + length - 1, y = row - 1}:
+                                                            Coordinates {x = column + length - 1, y = row + 1}:
+                                                            parseNumberPartNeighborsIn row column (length - 1)
+                                             | length == 0 = []
+
+parseNumberPartNeighbors :: Int -> Int -> Int -> [Coordinates]
+parseNumberPartNeighbors row column length = Coordinates {x = column - 1, y = row - 1}:
+                                             Coordinates {x = column - 1, y = row}:
+                                             Coordinates {x = column - 1, y = row+1}:
+                                             Coordinates {x = column + length, y = row - 1}:
+                                             Coordinates {x = column + length, y = row }:
+                                             Coordinates {x = column + length, y = row + 1}:
+                                             parseNumberPartNeighborsIn row column length
+
+parseNumberPartValue :: String -> String
+parseNumberPartValue (h: t) | isDigit h = h: parseNumberPartValue t
+parseNumberPartValue _ = []
+
+parseNumberPart :: Int -> Int -> String -> NumberPart
+parseNumberPart row column rawNumber = let value = parseNumberPartValue rawNumber
+                                           l = length value
+                                       in NumberPart {value = read value, numberLength = l,
+                                                      neighbors = parseNumberPartNeighbors row column l}
+
+parseLine :: Int -> Int -> String -> Engine -> Engine
+parseLine _ _ [] engine = engine
+parseLine row column (h: t) engine | isDigit h = let newNumberPart = parseNumberPart row column (h: t)
+                                                     newNumberLength = numberLength newNumberPart
+                                                 in parseLine row (column + newNumberLength) 
+                                                              (drop (newNumberLength - 1) t)
+                                                              engine {numbers = newNumberPart: numbers engine}
+                                   | h /= '.' = let newSymbolPart = SymbolPart {
+                                                                      symbol = h,
+                                                                      coordinates = Coordinates {x = column, y = row}
+                                                                    }
+                                                in parseLine row (column + 1) t
+                                                             engine {symbols = newSymbolPart: symbols engine}
+                                   | otherwise = parseLine row (column + 1) t engine
+
+parseEngine :: Int -> Engine -> IO Engine
+parseEngine row engine = do done <- isEOF
+                            if done
+                               then return engine
+                               else do line <- getLine
+                                       let newEngine = parseLine row 1 line engine
+                                       parseEngine (row+1) newEngine
+
+parse :: IO Engine
+parse = parseEngine 1 Engine {numbers = [], symbols = []}

day03/Main.hs

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+module Main where
+
+import Commons
+import qualified Part1
+import qualified Part2
+
+
+main = do engine <- parse
+          let part1Res = sum (Part1.getActualPartValuesNumbersFromEngine engine)
+          print part1Res
+          let part2Res = sum (Part2.getGearRatiosFromEngine engine)
+          print part2Res

day03/Part1.hs

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+module Part1 where
+
+import Commons
+
+
+isSymbolNeighbor :: [Coordinates] -> [Coordinates] -> Bool
+isSymbolNeighbor [] _ = False
+isSymbolNeighbor (h: t) symbolsCoordinates = h `elem` symbolsCoordinates || isSymbolNeighbor t symbolsCoordinates
+
+getActualPartNumbers :: [NumberPart] -> [Coordinates] -> [NumberPart]
+getActualPartNumbers [] _ = []
+getActualPartNumbers (h: t) symbolsCoordinates
+  | isSymbolNeighbor (neighbors h) symbolsCoordinates = h: getActualPartNumbers t symbolsCoordinates
+  | otherwise = getActualPartNumbers t symbolsCoordinates
+
+getActualPartValuesNumbersFromEngine :: Engine -> [Int]
+getActualPartValuesNumbersFromEngine engine =
+  map value (getActualPartNumbers (numbers engine) (map coordinates (symbols engine)))

day03/Part2.hs

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+module Part2 where
+
+import Commons
+
+
+getNumberNeighbors :: Coordinates -> [NumberPart] -> Int
+getNumberNeighbors _ [] = 0
+getNumberNeighbors symbolCoordinates (h: t)
+  | symbolCoordinates `elem` neighbors h = 1 + getNumberNeighbors symbolCoordinates t
+  | otherwise = getNumberNeighbors symbolCoordinates t
+
+isGear :: SymbolPart -> [NumberPart] -> Bool
+isGear symbolPart numberParts | symbol symbolPart == '*' = getNumberNeighbors (coordinates symbolPart) numberParts == 2
+                              | otherwise = False
+
+getRatioNeighbors :: Coordinates -> [NumberPart] -> Int
+getRatioNeighbors _ [] = 1
+getRatioNeighbors symbolCoordinates (h: t)
+  | symbolCoordinates `elem` neighbors h = value h * getRatioNeighbors symbolCoordinates t
+  | otherwise = getRatioNeighbors symbolCoordinates t
+
+getGearRatio :: SymbolPart -> [NumberPart] -> Int
+getGearRatio symbolPart numberParts
+  | isGear symbolPart numberParts = getRatioNeighbors (coordinates symbolPart) numberParts
+  | otherwise = 0
+
+getGearRatios :: [SymbolPart] -> [NumberPart] -> [Int]
+getGearRatios [] _ = []
+getGearRatios (h: t) numberParts = let gearRatio = getGearRatio h numberParts
+                                   in if gearRatio > 0
+                                         then gearRatio: getGearRatios t numberParts
+                                         else getGearRatios t numberParts
+
+getGearRatiosFromEngine :: Engine -> [Int]
+getGearRatiosFromEngine engine = getGearRatios (symbols engine) (numbers engine)