feat(day2): Fuck it we ball

day2/Main.hs

@@ -2,6 +2,8 @@ module Main where
 
 import System.Environment (getArgs)
 
+import Control.Exception (assert)
+
 import Text.Parsec (parse, many1, char, sepBy, endBy)
 import Text.Parsec.Char (endOfLine)
 import Text.ParserCombinators.Parsec (GenParser)
@@ -23,19 +25,28 @@ pairUp :: [a] -> [(a, a)]
 pairUp (a:b:tl) = (a, b) : pairUp (b:tl)
 pairUp _ = []
 
-allIncOrDec :: Report -> Bool
-allIncOrDec (a:b:tl)
-    | a /= b = all (uncurry (if a < b then (<) else (>))) $ pairUp $ b:tl
-    | otherwise = False
-allIncOrDec _ = True
+isSafe :: Report -> Bool
+isSafe (a:b:tl) = a /= b && (==) 0 (
+    length $ filter (not . (\(l, r) -> let
+                dif = abs (l - r)
+                cmp = if a < b then (<) else assert (b < a) (>)
+            in (1 <= dif) && (dif <= 3) && l `cmp` r))
+        $ pairUp
+        $ a:b:tl)
+isSafe _ = True
 
-notTooDifferent :: Report -> Bool
-notTooDifferent (a:b:tl) = let dif = abs (a - b)
-                           in (1 <= dif) && (dif <= 3) && notTooDifferent (b:tl)
-notTooDifferent _ = True
+with1Removed :: Report -> [Report]
+with1Removed (h:tl) = tl : map (h :) (with1Removed tl)
+with1Removed [] = []
+
+isKindaSafe :: Report -> Bool
+isKindaSafe = any isSafe . with1Removed
 
 part1 :: [Report] -> Int
-part1 = length . filter allIncOrDec . filter notTooDifferent
+part1 = length . filter isSafe
+
+part2 :: [Report] -> Int
+part2 = length . filter isKindaSafe
 
 main :: IO ()
 main = do
@@ -46,4 +57,4 @@ main = do
         Left e -> putStrLn ("Input file is incorrectly formatted : " ++ show e)
         Right r -> do
             putStrLn ("Solution (Part 1) : " ++ show (part1 r))
-            -- putStrLn ("Solution (Part 2) : " ++ show (part2 r))
+            putStrLn ("Solution (Part 2) : " ++ show (part2 r))