day 1

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

src/P1.hs

@@ -0,0 +1,35 @@
+module Main where
+
+import qualified AoC as A (count, extract)
+import Data.List (sort)
+import Text.Parsec (digit, many1, newline, parse, space, try)
+import Text.Parsec.String (Parser)
+
+parseLists :: Parser ([Int], [Int])
+parseLists =
+  unzip
+    -- multiple lines
+    <$> many1
+      ( (,)
+          -- first number
+          <$> (read <$> many1 digit)
+          -- second number
+          <*> (many1 space *> (read <$> many1 digit) <* try newline)
+      )
+
+part1 :: [Int] -> [Int] -> Int
+part1 xs ys = sum $ zipWith ((abs .) . (-)) xs ys
+
+part2 :: [Int] -> [Int] -> Int
+part2 xs ys = sum $ map (\x -> x * A.count x ys) xs
+
+main :: IO ()
+main =
+  do
+    raw <- readFile "./inputs/p1.in"
+    -- parse the input
+    let (xs', ys') = A.extract $ parse parseLists "" raw
+    -- sort the lists
+    let (xs, ys) = (sort xs', sort ys')
+    putStr "Part 1: " >> print (part1 xs ys)
+    putStr "Part 2: " >> print (part2 xs ys)