1 files changed, 30 insertions, 0 deletions
diff --git a/2020/04a.hs b/2020/04a.hs
new file mode 100644
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--- /dev/null
+++ b/2020/04a.hs
@@ -0,0 +1,30 @@
+module Day4a where
+
+import System.Environment (getArgs)
+import Data.List.Split (splitOn)
+
+-- Split a passport declaration into k:v declarations
+getDeclarations :: String -> [String]
+getDeclarations xs = concat [splitOn "\n" y | y <- splitOn " " xs]
+
+-- Split a passport declaration into tuples of (key, value)
+getTuples :: String -> [(String, String)]
+getTuples xs = [(head x, x!!1) | x <- map (splitOn ":") $ getDeclarations xs]
+
+-- Check a passport is valid
+passportValid :: String -> Bool
+passportValid xs = and [r `elem` map fst tups | r <- reqs]
+        where tups = getTuples xs
+              reqs = ["byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"]
+
+-- Usage: runghc --ghc-arg="-package split" 4a.hs inputs/day4
+main :: IO ()
+main = do 
+        args <- getArgs;
+        content <- readFile $ head args;
+
+        let ps = splitOn "\n\n" content;
+        let valid = filter passportValid ps;
+
+        print $ length valid;
+        return ();
+\ No newline at end of file