Day 03

day03/Part2.hs

@@ -0,0 +1,35 @@
+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)