feat: part 2-1

advent-of-code-2024.ipkg

@@ -14,4 +14,5 @@ executable = advent-of-code-2024
 main = Main
 modules = Main, Utils, AllDays,
           Data.Problem,
-          Day1.Part1, Day1.Part2
+          Day1.Part1, Day1.Part2,
+          Day2.Part1

src/AllDays.idr

@@ -2,3 +2,4 @@ module AllDays
 
 import public Day1.Part1
 import public Day1.Part2
+import public Day2.Part1

src/Day2/Part1.idr

@@ -0,0 +1,43 @@
+module Day2.Part1
+
+import Data.List
+import Data.List1
+import Data.String
+import Utils
+
+%default total
+
+--- TYPES
+
+public export
+Report : Type
+Report = List1 Nat
+
+--- PARSING
+
+parseLine : String -> Maybe Report
+parseLine = traverse parseNat . split (==' ')
+
+export
+parseInput : String -> Maybe (List Report)
+parseInput = traverse parseLine . lines
+
+--- DATA
+
+differences : Report -> List Integer
+differences ns =
+  let is = map natToInteger ns
+  in zipWith (-) (tail is) (forget is)
+
+export
+isSafe : Report -> Bool
+isSafe rep =
+  let diff = differences rep
+  in (all (>0) diff || all (<0) diff)
+      && all ((<=3) . abs) diff
+
+--- SOLUTION
+
+export
+solution : String -> Maybe Nat
+solution inp = count isSafe <$> parseInput inp

src/Main.idr

@@ -16,7 +16,7 @@ import AllDays
 ||| The latest problem that has been solved.
 -- NOTE: UPDATE AFTER EACH SOLUTION
 latest : Problem
-latest = Pr 1 Part2
+latest = Pr 2 Part1
 
 
 solMap : SortedMap Problem (String -> String)