107 lines
2.9 KiB
Agda
107 lines
2.9 KiB
Agda
module Day3
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import Prelude
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import Node
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import Aoc
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pfunc repr : {a : U} -> a -> String := `(a,o) => ''+o`
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pfunc jrepr : {a : U} -> a -> String := `(a,o) => JSON.stringify(o, null, ' ')`
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maybe : ∀ a b. b → (a → b) → Maybe a → b
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maybe def f Nothing = def
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maybe def f (Just a) = f a
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-- was 'structure' I could make a `record` that destructures to this..
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data Number : U where
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MkNumber : (start : Nat) -> (stop : Nat) → (value : Int) → Number
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numbers : List Char -> List Number
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numbers arr = go arr Z
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where
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go : List Char → Nat → List Number
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go (c :: cs) start = if isDigit c
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-- then let (front,back) = span isDigit (c :: cs) in ?
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then case span isDigit (c :: cs) of
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-- NOW FC on app is now broken, need the fc of the left
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(front,back) => let stop = start + length front
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in MkNumber start stop (stringToInt $ pack front) :: go back stop
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else go cs (S start)
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go Nil start = Nil
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range : ∀ a. Nat -> Nat -> List a -> List a
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range _ _ Nil = Nil
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range _ Z _ = Nil
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range Z (S k) (x :: xs) = x :: range Z k xs
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range (S n) (S m) (x :: xs) = range n m xs
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isPart : List (List Char) -> Nat -> Number -> Bool
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isPart rows row (MkNumber start end _) =
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checkRow (pred row) || checkRow row || checkRow (S row)
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where
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isThing : Char -> Bool
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isThing c = not (isDigit c || c == '.')
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checkRow : Nat -> Bool
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checkRow r = case getAt r rows of
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Nothing => False
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Just chars => case filter isThing (range (pred start) (S end) chars) of
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Nil => False
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_ => True
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getValue : Number -> Int
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getValue (MkNumber _ _ v) = v
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part1 : List (List Char) -> Int
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part1 rows =
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foldl (\ acc num => acc + getValue num) 0 $
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join $ map (partNums rows) $ enumerate rows
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where
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partNums : List (List Char) -> (Nat × List Char) -> List Number
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partNums grid (r, cs) =
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filter (isPart grid r) $ (numbers cs)
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gears : List (List Char) -> List Char -> Nat -> Int
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gears rows row y =
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let a = numbers (getAt! (pred y) rows)
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b = numbers (getAt! y rows)
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c = numbers (getAt! (S y) rows)
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all = a ++ b ++ c
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cands = map fst $ filter (_==_ '*' ∘ snd) (enumerate row)
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in foldl _+_ 0 $ map (check all) cands
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where
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ratio : List Int → Int
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ratio (a :: b :: Nil) = a * b
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ratio _ = 0
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match : Nat → Number → Bool
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match y (MkNumber start stop value) = pred start <= y && y < S stop
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check : List Number → Nat → Int
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check nums y = ratio $ map getValue (filter (match y) nums)
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part2 : List (List Char) -> Int
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part2 rows =
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foldl go 0 (enumerate rows)
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where
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go : Int → Nat × List Char → Int
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go acc (y, row) = acc + gears rows row y
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-- 4361 / 467835
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-- 517021 / 81296995
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run : String -> IO Unit
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run fn = do
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content <- readFile fn
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let grid = (splitOn '\n' $ unpack $ trim content)
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putStrLn fn
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printLn (part1 grid)
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printLn (part2 grid)
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main : IO Unit
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main = do
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run "aoc2023/day3/eg.txt"
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run "aoc2023/day3/input.txt"
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