55 lines
1.4 KiB
Agda
55 lines
1.4 KiB
Agda
module Day1
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import Prelude
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import Node
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parseLine : String → Maybe Int
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parseLine s = case unpack s of
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('L' :: rest) => Just $ 0 - stringToInt (pack rest)
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('R' :: rest) => Just $ stringToInt (pack rest)
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_ => Nothing
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parse : String → List Int
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parse text = mapMaybe parseLine $ split (trim text) "\n"
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part1 : List Int → Int
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part1 xs = go 0 50 xs
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where
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go : Int → Int → List Int → Int
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go acc pos Nil = acc
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go acc pos (x :: xs) =
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let pos = mod (x + pos) 100
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acc = if pos == 0 then acc + 1 else acc
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in go acc pos xs
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-- This is uglier than I'd like
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part2 : List Int → Nat
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part2 xs = go Z 50 xs
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where
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go : Nat → Int → List Int → Nat
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go acc pos Nil = acc
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go acc pos (0 :: xs) = go acc pos xs
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go acc pos (x :: xs) =
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if x == 0 then go acc pos xs
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else if x <= -100 then go (S acc) pos (x + 100 :: xs)
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else if 100 <= x then go (S acc) pos (x - 100 :: xs)
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else if x + pos < 0 then go (if pos == 0 then acc else S acc) (x + pos + 100) xs
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else if x + pos == 0 then go (S acc) (x + pos) xs
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else if 100 <= x + pos then go (S acc) (x + pos - 100) xs
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else go acc (x + pos) xs
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run : String → IO Unit
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run fn = do
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printLn fn
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text <- readFile fn
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let xs = parse text
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let p1 = part1 xs
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printLn "part1 \{show p1}"
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let p2 = part2 xs
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printLn "part2 \{show p2}"
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main : IO Unit
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main = do
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run "aoc2025/day1/eg.txt"
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run "aoc2025/day1/input.txt"
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