day 10

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

README

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+My advent of code solutions for 2022. I am trying to not use String wherever possible and use Data.Text instead. That makes the programs appear bigger than they are LOC-wise.

day10.hs

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+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ViewPatterns #-}
+
+import Data.Text (Text)
+import qualified Data.Text as T (lines, pack, unlines, words)
+import qualified Data.Text.IO as T (putStr)
+import qualified Data.Text.Read as T (decimal, signed)
+import Lib (readFile')
+
+main :: IO ()
+main = do
+  vals <-
+    scanl1 (+)
+      . reverse
+      . foldl
+        ( \xs x ->
+            let o : n = T.words x
+                dec (T.signed T.decimal . head -> Right (m, "")) = m
+             in if o == "noop" then 0 : xs else dec n : 0 : xs
+        )
+        [1]
+      . T.lines
+      <$> readFile' "day10.in"
+  putStr "Q1: "
+  print $ q1 vals
+  putStrLn "Q2: "
+  T.putStr $ q2 vals
+
+q1 :: [Int] -> Int
+q1 v = foldr (\x xs -> xs + (v !! (x - 1) * x)) 0 [20, 60 .. 220]
+
+q2 :: [Int] -> Text
+q2 v =
+  T.unlines $
+    map
+      ( \x ->
+          T.pack $
+            map (\y -> if abs (v !! (x + y) - y) <= 1 then '#' else '.') [0 .. 39]
+      )
+      [0, 40 .. 200]

day9.hs

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+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ViewPatterns #-}
+
+import Data.List (nub, scanl)
+import Data.Text (Text)
+import qualified Data.Text as T (lines, unpack, words)
+import qualified Data.Text.Read as T (decimal)
+import Lib (readFile')
+
+-- a rather slow program, takes 300 ms on my system (with `time`, but idc anymore 😭
+
+main :: IO ()
+main = do
+  input <-
+    concatMap
+      ((\[T.unpack -> [d], T.decimal -> Right (n, "")] -> replicate n d) . T.words)
+      . T.lines
+      <$> readFile' "day9.in"
+  putStr "Q1: "
+  print $ q 1 input
+  putStr "Q2: "
+  print $ q 9 input
+
+moveHead :: Char -> (Int, Int) -> (Int, Int)
+moveHead d (x, y) = case d of
+  'L' -> (x - 1, y)
+  'R' -> (x + 1, y)
+  'U' -> (x, y + 1)
+  'D' -> (x, y - 1)
+
+moveTail :: (Int, Int) -> (Int, Int) -> (Int, Int)
+moveTail (hx, hy) (tx, ty)
+  | abs dx <= 1 && abs dy <= 1 = (tx, ty) -- dont move
+  | abs dx > abs dy = (tx + signum dx, hy) -- move horizontally
+  | abs dy > abs dx = (hx, ty + signum dy) -- move vertically
+  | otherwise = (tx + signum dx, ty + signum dy ) -- move diagonally
+  where
+    dx = hx - tx
+    dy = hy - ty
+
+q :: Int -> [Char] -> Int
+q n =
+  length . nub . map last
+    . scanl
+      ( \(h : t) d ->
+          reverse $ foldl (\(h : xs) x -> moveTail h x : (h : xs)) [moveHead d h] t
+      )
+      (replicate (n + 1) (0, 0))