day 3 part 2 with no tidying yet!

Aoc2024/Day03/Main.lean

@@ -5,7 +5,7 @@ def solve (name: String) (inputPath: String) : IO Unit := do
   IO.println name
   let input <- IO.FS.readFile inputPath
   IO.println s!"Part 1: {solvePart1 input}"
-  -- IO.println s!"Part 2: {<- parseAndSolvePart2 input}"
+  IO.println s!"Part 2: {solvePart2 input}"
 
 def main : IO Unit := do
   IO.println "Day 03"

Aoc2024/Day03/Solve.lean

@@ -6,40 +6,58 @@ open Regex (Match Captures)
 
 inductive Instruction where
   | mul (n m : Nat) : Instruction
-  -- | do : Instruction
-  -- | dont: Instruction
+  | do : Instruction
+  | dont: Instruction
 deriving instance BEq, Hashable, Repr for Instruction
 
-def mulRegex: Regex := regex% r"mul\((\d+),(\d+)\)"
+def instructionRegex: Regex := regex% r"mul\((\d+),(\d+)\)|do\(\)|don't\(\)"
 
 def matchToNat (m : Match) : Option Nat := m.toNat?
 
 def optMatchToNat (m : Option Match) : Option Nat := m >>= matchToNat
 
-def matchesToNatPair (ms : Array (Option Match)): Option Instruction :=
+def matchesToInstruction (ms : Array (Option Match)): Option Instruction :=
   match ms.toList with
   | [some m1, some m2] => Instruction.mul <$> matchToNat m1 <*> matchToNat m2
   | _ => none
 
-def capturesToNatPair (captures: Captures) : Option Instruction :=
-  matchesToNatPair captures.groups
+def capturesToInstruction (captures: Captures) : Option Instruction :=
+  if captures.fullMatch == "do()" then some Instruction.do
+  else if captures.fullMatch == "don't()" then some Instruction.dont
+  else matchesToInstruction captures.groups
 
-def findMatches (s : String) : List Instruction :=
-  Regex.all_captures s mulRegex |>.toList |>.bind (fun captures => captures |> capturesToNatPair |> Option.toList)
+def findInstructions (s : String) : List Instruction :=
+  Regex.all_captures s instructionRegex |>.toList |>.bind (fun captures => captures |> capturesToInstruction |> Option.toList)
 
-#guard findMatches "mul(1,2) mul(3,4)" == [Instruction.mul 1 2, Instruction.mul 3 4]
+#guard findInstructions "mul(1,2) mul(3,4)" == [Instruction.mul 1 2, Instruction.mul 3 4]
+#guard findInstructions "do()" == [Instruction.do]
+#guard findInstructions "don't()" == [Instruction.dont]
 
-def solvePart1 (s : String) : Int := findMatches s |>.sumBy (fun
+def solvePart1 (s : String) : Int := findInstructions s |>.sumBy (fun
   | Instruction.mul n m => n * m
+  | _ => 1
 )
 
 #guard solvePart1 exampleInput = 161
 
-private def solvePart2 (things : List Int) : Int := sorry
+private def filterInstructions (enabled : Bool) : List Instruction -> List Instruction
+  | List.nil => []
+  | List.cons (Instruction.mul m n) rest =>
+    if enabled then List.cons (Instruction.mul m n) (filterInstructions enabled rest)
+   else filterInstructions enabled rest
+  | List.cons Instruction.do rest => filterInstructions true rest
+  | List.cons Instruction.dont rest => filterInstructions false rest
 
-def instrRegex := regex% r"mul\((\d+),(\d+)\)|do()\)"
-#eval Regex.all_captures "mul(1,2) do()" instrRegex
+#eval findInstructions "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))" |> filterInstructions true
+
+def solvePart2 (s : String) : Int := s |> findInstructions |> filterInstructions true |> List.sumBy (fun
+  | Instruction.mul n m => n * m
+  | _ => 1
+)
+
+#eval solvePart2 "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))"
+
+#guard solvePart2 "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))" == 48
 
-def parseAndSolvePart2 (s : String): Except String Int := parseThings s |>.map solvePart2
 
 -- #guard parseAndSolvePart2 exampleInput == Except.ok 4