subtree(users/wpcarro): docking briefcase at '24f5a642' r/3226

git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c09813172c79820bcf526bb10cf4208
git-subtree-split: 24f5a642af3aa1627bbff977f0a101907a02c69f
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789

1 files changed, 52 insertions, 0 deletions

diff --git a/users/wpcarro/assessments/brilliant/Transforms.hs b/users/wpcarro/assessments/brilliant/Transforms.hs
new file mode 100644
index 000000000000..d8df8f8372e0
--- /dev/null
+++ b/users/wpcarro/assessments/brilliant/Transforms.hs
@@ -0,0 +1,52 @@
+--------------------------------------------------------------------------------
+module Transforms where
+--------------------------------------------------------------------------------
+import Control.Applicative ((<|>))
+import Text.ParserCombinators.ReadP
+--------------------------------------------------------------------------------
+
+data Transform = VerticalFlip
+               | HorizontalFlip
+               | Shift Int
+               deriving (Eq, Show)
+
+digit :: ReadP Char
+digit =
+  satisfy (\c -> c >= '0' && c <= '9')
+
+command :: ReadP Transform
+command = vertical
+      <|> horizontal
+      <|> shift
+  where
+    vertical =
+      char 'V' >> pure VerticalFlip
+
+    horizontal =
+      char 'H' >> pure HorizontalFlip
+
+    shift = do
+      _ <- char 'S'
+      negative <- option Nothing $ fmap Just (satisfy (== '-'))
+      n <- read <$> many1 digit
+      case negative of
+        Nothing -> pure $ Shift n
+        Just _  -> pure $ Shift (-1 * n)
+
+-- | Attempt to remove redundant transformations.
+-- | Here are some rules that I'd like to support but may not have time for:
+-- | - All even-numbered flips (w/o intermittent shifts) can become zero
+-- | - All odd-numbered flips (w/o intermittent shifts) can become 1
+-- | - All shifts can be be reduce to the absolute value of shifts
+optimize :: [Transform] -> [Transform]
+optimize [] = []
+optimize [x] = [x]
+optimize (VerticalFlip:VerticalFlip:xs) = optimize xs
+optimize (HorizontalFlip:HorizontalFlip:xs) = optimize xs
+optimize xs = xs
+
+fromString :: String -> Maybe [Transform]
+fromString x =
+  case readP_to_S (manyTill command eof) x of
+   [(res, "")] -> Just res
+   _           -> Nothing