Day 8

day08/Part2.hs

@@ -0,0 +1,21 @@
+module Part2 where
+
+import Commons
+import Data.HashMap.Internal.Strict (keys, (!))
+
+
+getStarts :: [(String, Instruction)] -> [String]
+getStarts [] = []
+getStarts (([a, b, 'A'], ILeft): t) = [a, b, 'A']: getStarts t
+getStarts (_: t) = getStarts t
+
+getDistanceToEnd :: [Instruction] -> Network -> String -> Int
+getDistanceToEnd [] network start = getDistanceToEnd (instructions network) network start
+getDistanceToEnd  _ _ [_, _, 'Z'] = 0
+getDistanceToEnd (ih: t) network start = 1 + getDistanceToEnd t network (nodes network ! (start, ih))
+
+getAllDistances :: Network -> [Int]
+getAllDistances network = map (getDistanceToEnd [] network) . getStarts . keys $ nodes network
+
+getSteps :: Network -> Int
+getSteps = foldr lcm 1 . getAllDistances