Done day 9

[advent-of-code-20.git] / advent09 / src / advent09.hs

diff --git a/advent09/src/advent09.hs b/advent09/src/advent09.hs
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+-- import Debug.Trace
+
+import Data.List
+
+main :: IO ()
+main = 
+    do  numStrs <- readFile "data/advent09.txt"
+        let nums = map (read @Int) $ lines numStrs
+        let firstInvalid = part1 nums
+        print firstInvalid
+        print $ part2 firstInvalid nums
+        -- print $ head $ part2 nums
+
+part1 nums = fst $ head $ filter (not . valid) $ slidingWindow 25 nums
+
+slidingWindow winSize nums = 
+    zip (drop winSize nums) $ map (take winSize) $ tails nums
+
+valid (target, window) = not $ null [(x, y) | x <- window, y <- window, x + y == target]
+
+
+part2 target nums = (maximum section) + (minimum section)
+    where section = head $ filter (sumsToTarget target) $ subStrings nums
+
+-- subStrings :: [a] -> [[a]]
+subStrings = (concatMap inits) . tails
+
+-- sumsToTarget :: Int -> [Int] -> Bool
+sumsToTarget target ns = sum ns == target
+