Day 4

day04/Part2.hs

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+module Part2 where
+
+import Commons
+
+
+getNWinningNumbers :: [Int] -> [Int] -> Int
+getNWinningNumbers _ [] = 0
+getNWinningNumbers winningNumbers (n: t) | n `elem` winningNumbers = 1 + getNWinningNumbers winningNumbers t
+                                         | otherwise = getNWinningNumbers winningNumbers t
+
+updateNCopies :: Int -> Card -> [Card] -> [Card]
+updateNCopies 0 card otherCards = otherCards
+updateNCopies n card (c: t) = c {nCopies = nCopies card + nCopies c}: updateNCopies (n - 1) card t
+
+updateCopies :: Card -> [Card] -> [Card]
+updateCopies card otherCards = let nWinningNumbers = getNWinningNumbers (winningNumbers card) (numbers card)
+                               in updateNCopies nWinningNumbers card otherCards
+
+updateAllCopies :: [Card] -> [Card]
+updateAllCopies [] = []
+updateAllCopies (c: t) = c: updateAllCopies (updateCopies c t)
+
+getNCopies :: [Card] -> [Int]
+getNCopies cards = map nCopies (updateAllCopies cards)