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import Common
namespace Day2
structure Draw (α : Type) where
red : α
green : α
blue : α
deriving Repr
structure Game where
id : Nat
draw : List $ Draw Nat
deriving Repr
def parse (input : String) : Option $ List Game :=
let lines := input.splitTrim (. == '\n')
let lines := lines.filter (not ∘ String.isEmpty)
let parse_single_line : (String → Option Game):= λ (l : String) ↦ do
let parse_id := λ (s : String) ↦ do
let rest ← if s.startsWith "Game " then some (s.drop 5) else none
rest.toNat?
let parse_draw := λ (s : String) ↦ do
let s := s.splitTrim (· == ',')
let findAndRemoveTail := λ (s : String) (t : String) ↦
if s.endsWith t then
some $ String.dropRight s (t.length)
else
none
let update_draw_parse := λ (pd : Option (Draw (Option String))) (c : String) ↦ do
let old ← pd
let red := findAndRemoveTail c " red"
let green := findAndRemoveTail c " green"
let blue := findAndRemoveTail c " blue"
match red, green, blue with
| some red, none, none => match old.red with
| none => some $ {old with red := some red}
| some _ => none
| none, some green, none => match old.green with
| none => some $ {old with green := some green}
| some _ => none
| none, none, some blue => match old.blue with
| none => some $ {old with blue := some blue}
| some _ => none
| _, _, _ => none
let parsed_draw ← s.foldl update_draw_parse (some $ Draw.mk none none none)
let parsed_draw := {
red := String.toNat? <$> parsed_draw.red,
green := String.toNat? <$> parsed_draw.green,
blue := String.toNat? <$> parsed_draw.blue : Draw _}
let extractOrFail := λ (s : Option $ Option Nat) ↦ match s with
| none => some 0
| some none => none
| some $ some x => some x
let red ← extractOrFail parsed_draw.red
let green ← extractOrFail parsed_draw.green
let blue ← extractOrFail parsed_draw.blue
pure { red := red, blue := blue, green := green : Draw _}
let parse_draws := λ s ↦ List.mapM parse_draw $ s.splitTrim (· == ';')
let (id, draw) ← match l.splitTrim (· == ':') with
| [l, r] => Option.zip (parse_id l) (parse_draws r)
| _ => none
pure { id := id, draw := draw}
lines.mapM parse_single_line
def part1 (games : List Game) : Nat :=
let draw_possible := λ g ↦ g.red ≤ 12 && g.green ≤ 13 && g.blue ≤ 14
let possible := flip List.all draw_possible
let possible_games := games.filter (possible ∘ Game.draw)
possible_games.map Game.id |> List.foldl Nat.add 0
def part2 (games : List Game) : Nat :=
let powerOfGame := λ (g : Game) ↦
let minReq := λ (c : Draw Nat → Nat) ↦
g.draw.map c |> List.max? |> flip Option.getD 0
minReq Draw.red * minReq Draw.green * minReq Draw.blue
let powers := games.map powerOfGame
powers.foldl Nat.add 0
open DayPart
instance : Parse ⟨2, by simp⟩ (ι := List Game) where
parse := (λ o ↦ match o with | some a => pure a | none => throw "Failed to parse input") ∘ parse
instance : Part ⟨2,_⟩ Parts.One (ι := List Game) (ρ := Nat) where
run := some ∘ part1
instance : Part ⟨2,_⟩ Parts.Two (ι := List Game) (ρ := Nat) where
run := some ∘ part2
def testInput : String :=
"Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green
Game 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue
Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red
Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red
Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green"
-- #eval part1 <$> parse testInput
-- #eval part2 <$> parse testInput
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