fix: remove out-of-bound/Maybe from day 2 part 2
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2 changed files with 7 additions and 12 deletions
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@ -3,3 +3,7 @@
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## Part 1
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Spent some time reading up on how to define a custom instance of `Read`. Pretty simple otherwise. Surprised `countElem` isn't in Prelude.
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## Part 2
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Off-by-one errors were called out in the puzzle but I still made them. ~Solution can be simplified if I don't need to check for out-of-bounds issues.~ I did this.
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@ -25,21 +25,12 @@ solve = show . length . filter (isValidPasswordEntry . readPasswordEntry) . line
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readPasswordEntry :: String -> PasswordEntry
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readPasswordEntry = read
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(!!?) :: [a] -> Int -> Maybe a
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[] !!? _ = Nothing
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(x:xs) !!? 0 = Just x
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(_:xs) !!? idx = xs !!? (idx - 1)
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maybeToBool (Just a) = a
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maybeToBool Nothing = False
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xor :: Bool -> Bool -> Bool
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xor l r = l /= r
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isValidPasswordEntry (PasswordEntry pos1 pos2 char pass) =
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(maybeToBool $ fmap (==char) char1) `xor`
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(maybeToBool $ fmap (==char) char2)
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(charAtPos1 == char) `xor` (charAtPos2 == char)
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where
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char1 = pass !!? (pos1 - 1)
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char2 = pass !!? (pos2 - 1)
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charAtPos1 = pass !! (pos1 - 1)
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charAtPos2 = pass !! (pos2 - 1)
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