feat: part 2-2

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, Day2.Part2

src/AllDays.idr

@@ -2,3 +2,5 @@ module AllDays
 
 import public Day1.Part1
 import public Day1.Part2
+import public Day2.Part1
+import public Day2.Part2

src/Day1/Part1.idr

@@ -20,7 +20,7 @@ export
 parseInput : String -> Maybe (List Nat, List Nat)
 parseInput = map unzip . traverse parseLine . lines
 
---- UTILS
+--- DATA
 
 distance : Nat -> Nat -> Nat
 distance x y =

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/Day2/Part2.idr

@@ -0,0 +1,27 @@
+module Day2.Part2
+
+import Data.List
+import Data.List1
+import Data.String
+import Utils
+
+import Day2.Part1
+
+%default total
+
+--- DATA
+
+reductions : Report -> List Report
+reductions (x ::: []) = []
+reductions (x ::: [y]) = [y ::: [], x ::: []]
+reductions (x ::: (y :: xs)) =
+  (y ::: xs) :: map (x `cons`) (assert_total $ reductions (y ::: xs))
+
+isSafe' : Report -> Bool
+isSafe' rep = isSafe rep || any isSafe (reductions rep)
+
+--- SOLUTION
+
+export
+solution : String -> Maybe Nat
+solution inp = count isSafe' <$> parseInput inp

src/Main.idr

@@ -1,10 +1,12 @@
 module Main
 
 import Data.List1
+import Data.Maybe
 import Data.String
 import Data.SortedMap
 import Data.SortedMap.Dependent
 import Data.Problem
+import Utils
 
 import Language.Reflection
 
@@ -16,7 +18,7 @@ import AllDays
 ||| The latest problem that has been solved.
 -- NOTE: UPDATE AFTER EACH SOLUTION
 latest : Problem
-latest = Pr 1 Part2
+latest = Pr 2 Part2
 
 
 solMap : SortedMap Problem (String -> String)