initial commit

1 files changed, 28 insertions, 0 deletions

diff --git a/2020/1b.hs b/2020/1b.hs
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index 0000000..6cebb47
--- /dev/null
+++ b/2020/1b.hs
@@ -0,0 +1,28 @@
+module Day1 where
+
+import Text.Read (readMaybe)
+import System.Environment (getArgs)
+
+-- All 3-tuples you can take from a list (where ordering doesn't matter)
+cp3 :: [a] -> [(a, a, a)]
+cp3 [] = []
+cp3 (x:xs) = [(x, y, z) | y <- xs, z <- xs] ++ cp3 xs
+
+getSomes :: [Maybe a] -> [a]
+getSomes xs = [x | Just x <- xs]
+
+sumEq :: Int -> [Int] -> [(Int, Int, Int)]
+sumEq target = filter (\(x,y,z) -> x + y + z == target) . cp3
+
+main :: IO ()
+main = do 
+        args <- getArgs;
+        content <- readFile $ head args;
+        let l = lines content;
+        let nums = getSomes $ map readMaybe l :: [Int]
+
+        let (a,b,c) = head $ sumEq 2020 nums;
+        let r = a * b * c;
+
+        putStrLn $ show a ++ " + " ++ show b ++ " + " ++ show c ++ " = 2020";
+        putStrLn $ show a ++ " * " ++ show b ++ " * " ++ show c ++ " = " ++ show r;
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