66 lines
1.6 KiB
Agda
66 lines
1.6 KiB
Agda
module Day2
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import Prelude
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import Node
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import Aoc
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parse : String → List (Int × Int)
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parse text = map mkPair $ split text ","
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where
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mkPair : String → Int × Int
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mkPair t = case split t "-" of
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(a :: b :: Nil) => (stringToInt a, stringToInt b)
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bad => fatalError "BAD \{t}"
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invalid : Int → Bool
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invalid n =
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let s = show n
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l = slen s
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h = l / 2
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in if h * 2 /= l then False
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else go s 0 h
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where
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go : String → Int → Int → Bool
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go s i h = if i == h
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then True
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else if sindex s i == sindex s (i + h) then go s (i + 1) h else False
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match : Int → Int → Bool
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match f n = let v = mod n f in if v * 10 < f then False else go v n
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where
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go : Int → Int → Bool
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go pat 0 = True
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go pat n = if (mod n f) /= pat then False else go pat (n / f)
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invalid2 : Int → Bool
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invalid2 s = go 10 s
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where
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go : Int → Int → Bool
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go f n =
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if f * f > n * 10 then False
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else if match f n then True
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else go (f * 10) n
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scan : (Int → Bool) → Int → Int → Int → Int
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scan invalid a b acc =
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let acc = if invalid a then acc + a else acc in
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if a == b then acc else scan invalid (a + 1) b acc
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part1 : String → Int
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part1 text = foldl (\acc x => scan invalid (fst x) (snd x) acc) 0 $ parse text
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part2 : String → Int
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part2 text = foldl (\acc x => scan invalid2 (fst x) (snd x) acc) 0 $ parse text
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run : String -> IO Unit
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run fn = do
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putStrLn fn
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text <- readFile fn
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putStrLn $ "part1 " ++ show (part1 text)
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putStrLn $ "part2 " ++ show (part2 text)
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main : IO Unit
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main = do
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run "aoc2025/day2/eg.txt"
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run "aoc2025/day2/input.txt"
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