Day 3

Day1/puzzle1.hs

@@ -7,5 +7,4 @@ listDistance xs ys = sum $ map abs $ zipWith (-) (sort xs) (sort ys)
 main = do
     contents <- lines <$> readFile "day1.txt"
     let [x, y] = transpose $ map read . words <$> contents
-        distance = listDistance x y
-    print distance
+    print $ listDistance x y

Day1/puzzle2.hs

@@ -8,5 +8,4 @@ similarityScore xs ys = let elemsY = [ (head y, length y) | y <- (group . sort)
 main = do
     contents <- lines <$> readFile "day1.txt"
     let [x, y] = transpose $ map read . words <$> contents
-        score = similarityScore x y
-    print score
+    print $ similarityScore x y

Day2/puzzle1.hs

@@ -10,5 +10,4 @@ isSafe xs = (isAscending xs || isDescending xs) && maximum distances <= 3 && min
 main = do
     contents <- lines <$> readFile "day2.txt"
     let reports = map read . words <$> contents
-        safeCount = length $ filter isSafe reports
-    print safeCount
+    print . length $ filter isSafe reports

Day2/puzzle2.hs

@@ -15,5 +15,4 @@ removeLevel xs = zipWith (++) ys zs
 main = do
     contents <- lines <$> readFile "day2.txt"
     let reports = map read . words <$> contents
-        safeCount = length . filter (any isSafe) $ map removeLevel reports
-    print safeCount
+    print . length . filter (any isSafe) $ map removeLevel reports

Day3/puzzle1.hs

@@ -0,0 +1,12 @@
+import Data.List.Split (splitOn)
+import Data.Char (isDigit)
+import Text.Regex.TDFA (getAllTextMatches, (=~))
+
+sumMul :: [String] -> Int
+sumMul xs = let vals = map (splitOn "," . filter (`elem` "0123456789,")) xs
+            in  sum $ map (product . map read) vals
+
+main = do
+    contents <- readFile "day3.txt"
+    let mults = getAllTextMatches (contents =~ "mul\\([0-9]+,[0-9]+\\)") :: [String]
+    print $ sumMul mults

Day3/puzzle2.hs

@@ -0,0 +1,16 @@
+import Data.List (isPrefixOf)
+import Data.List.Split (split, splitOn, startsWith)
+import Data.Char (isDigit)
+import Text.Regex.TDFA (getAllTextMatches, (=~))
+
+sumMul :: [String] -> Int
+sumMul xs = let vals = map (splitOn "," . filter (`elem` "0123456789,")) xs
+            in  sum $ map (product . map read) vals
+
+filterDonts :: [String] -> String
+filterDonts = concat . filter (not . isPrefixOf "don't()") . concatMap (split (startsWith "do()"))
+
+main = do
+    contents <- split (startsWith "don't()") <$> readFile "day3.txt"
+    let mults = getAllTextMatches (filterDonts contents =~ "mul\\([0-9]+,[0-9]+\\)") :: [String]
+    print $ sumMul mults