initial commit

1 files changed, 28 insertions, 0 deletions

diff --git a/2020/1a.hs b/2020/1a.hs
new file mode 100644
index 0000000..adac6bc
--- /dev/null
+++ b/2020/1a.hs
@@ -0,0 +1,28 @@
+module Day1 where
+
+import Text.Read (readMaybe)
+import System.Environment (getArgs)
+
+-- Cartesian product of a set with itself where ordering doesn't matter
+cp :: [a] -> [(a, a)]
+cp [] = []
+cp (x:xs) = [(x, y) | y <- xs] ++ cp xs 
+
+getSomes :: [Maybe a] -> [a]
+getSomes xs = [x | Just x <- xs]
+
+sumEq :: Int -> [Int] -> [(Int, Int)]
+sumEq target = filter (\(x,y) -> x + y == target) . cp
+
+main :: IO ()
+main = do 
+        args <- getArgs;
+        content <- readFile $ head args;
+        let l = lines content;
+        let nums = getSomes $ map readMaybe l :: [Int]
+
+        let (a,b) = head $ sumEq 2020 nums;
+        let r = a * b;
+
+        putStrLn $ show a ++ " + " ++ show b ++ " = 2020";
+        putStrLn $ show a ++ " * " ++ show b ++ " = " ++ show r;
\ No newline at end of file