Day 5

Day2/puzzle1.hs

@@ -2,9 +2,9 @@ import Data.List (sort)
 
 isSafe :: [Int] -> Bool
 isSafe xs = (isAscending xs || isDescending xs) && maximum distances <= 3 && minimum distances >= 1
-            where isAscending xs = xs == sort xs
+            where isAscending xs  = xs == sort xs
                   isDescending xs = xs == reverse (sort xs)
-                  distances = map abs $ zipWith (-) xs (tail xs)
+                  distances       = map abs $ zipWith (-) xs (tail xs)
 
 main = do
     contents <- lines <$> readFile "day2.txt"

Day4/puzzle1.hs

@@ -9,12 +9,12 @@ countSubstrings :: String -> [String] -> Int
 countSubstrings word text = sum (map (countSubstrings' word) text) + sum (map (countSubstrings' word . reverse) text)
                             + sum (map (countSubstrings' word) cols) + sum (map (countSubstrings' word . reverse) cols)
                             + sum (map (countSubstrings' word) diags) + sum (map (countSubstrings' word . reverse) diags)
-                            where cols = transpose text
+                            where cols  = transpose text
                                   diags = diagonals text
                                   countSubstrings' _ [] = 0
                                   countSubstrings' word text@(_:rest) = if word `isPrefixOf` text
-                                                                               then 1 + countSubstrings' word rest
-                                                                               else countSubstrings' word rest
+                                                                           then 1 + countSubstrings' word rest
+                                                                           else countSubstrings' word rest
     
 main = do
     contents <- lines <$> readFile "day4.txt"

Day4/puzzle2.hs

@@ -10,8 +10,8 @@ countSubstrings word text = sum (map (countSubstrings' word) diags) + sum (map (
                             where diags = diagonals text
                                   countSubstrings' _ [] = 0
                                   countSubstrings' word text@(_:rest) = if word `isPrefixOf` text
-                                                                        then 1 + countSubstrings' word rest
-                                                                        else countSubstrings' word rest
+                                                                           then 1 + countSubstrings' word rest
+                                                                           else countSubstrings' word rest
 
 submatricesVert :: Int -> [String] -> [[String]]
 submatricesVert _ [] = []

Day5/puzzle1.hs

@@ -0,0 +1,16 @@
+import Data.List.Split (splitOn)
+
+isSorted :: [(String, String)] -> [String] -> Bool
+isSorted rules [x] = True
+isSorted rules (x:xs) = let after = [ p | (p, n) <- rules, n == x ]
+                        in  not (any (`elem` after) xs) && isSorted rules xs
+
+getMiddle :: [String] -> String
+getMiddle xs = xs !! (length xs `div` 2)
+
+main = do
+    contents <- map (splitOn "|") . lines <$> readFile "day5.txt"
+    let rules = [ (x, y) | [x, y] <- takeWhile (/= [""]) contents ]
+        updates = concatMap (map (splitOn ",")) . tail $ dropWhile (/= [""]) contents
+        sorted = filter (isSorted rules) updates
+    print . sum $ map (read . getMiddle) sorted

Day5/puzzle2.hs

@@ -0,0 +1,24 @@
+import Data.List ((\\))
+import Data.List.Split (splitOn)
+
+isSorted :: [(Int, Int)] -> [Int] -> Bool
+isSorted rules [x] = True
+isSorted rules (x:xs) = let after = [ p | (p, n) <- rules, n == x ]
+                        in  not (any (`elem` after) xs) && isSorted rules xs
+
+getMiddle :: [Int] -> Int 
+getMiddle xs = xs !! (length xs `div` 2)
+
+sortOnRules :: [(Int, Int)] -> [Int] -> [Int]
+sortOnRules _ [] = []
+sortOnRules rules (x:xs) = sortOnRules rules beforeArray ++ [x] ++ sortOnRules rules afterArray
+                            where afterArray = xs \\ before
+                                  beforeArray  = xs \\ afterArray
+                                  before      = [ p | (p, n) <- rules, n  == x ]
+
+main = do
+    contents <- map (splitOn "|") . lines <$> readFile "day5.txt"
+    let rules = [ (read x, read y) | [x, y] <- takeWhile (/= [""]) contents ]
+        unsorted = filter (not . isSorted rules) . map (map read) $ concatMap (map (splitOn ",")) . tail $ dropWhile (/= [""]) contents
+        fixUnsorted = map (sortOnRules rules) unsorted
+    print . sum $ map getMiddle fixUnsorted