Done day 2

diff --git a/advent02/Main.hs b/advent02/Main.hs
new file mode 100644 (file)
index 0000000..a0f4534
--- /dev/null
+++ b/advent02/Main.hs
@@ -0,0 +1,38 @@
+-- Writeup at https://work.njae.me.uk/2024/12/02/advent-of-code-2024-day-2/
+
+import AoC
+import Data.List
+
+main :: IO ()
+main = 
+  do  dataFileName <- getDataFileName
+      text <- readFile dataFileName
+      let reports = fmap readLine $ lines text
+      print $ part1 reports
+      print $ part2 reports
+
+part1, part2 :: [[Int]] -> Int
+part1 reports = length $ filter isSafe reports
+part2 reports = length $ filter isSafe' reports
+    where isSafe' l = isSafe l || safeWhenDamped l
+
+isSafe, allSameSign, bigEnough, smallEnough, safeWhenDamped :: [Int] -> Bool
+isSafe xs = allSameSign diffs && bigEnough diffs && smallEnough diffs
+  where diffs = zipWith (-) xs (tail xs)
+
+allSameSign xs 
+ | all (>0) xs = True
+ | all (<0) xs = True
+ | otherwise = False
+
+bigEnough = all ((>= 1) . abs)
+smallEnough = all ((<= 3) . abs)
+
+safeWhenDamped = (any isSafe) . damped
+
+damped :: [Int] -> [[Int]]
+damped line = zipWith (++) (inits line) (drop 1 $ tails line)
+
+readLine :: String -> [Int]
+readLine = (fmap read) . words
+

diff --git a/adventofcode24.cabal b/adventofcode24.cabal
index f922676e08e28f7f446eca89b4fd6b681cb0fb4a..565d1d98839ca839dca8ec3113bd7911383ddecd 100644 (file)
--- a/adventofcode24.cabal
+++ b/adventofcode24.cabal
@@ -76,3 +76,8 @@ executable advent01
   import: warnings, common-extensions, build-directives, common-modules
   main-is: advent01/Main.hs
   build-depends: multiset
+
+executable advent02
+  import: warnings, common-extensions, build-directives, common-modules
+  main-is: advent02/Main.hs
+  
\ No newline at end of file