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newtype Keypad = Keypad [String] | |
defaultPad = Keypad [ | |
"1", "abc2", "def3", | |
"ghi4", "jkl5", "mno6", | |
"pqrs7", "tuv8", "wxyz9", | |
"^*", "+_0", ".,#"] | |
-- | Replace capital characters with * and lowered character | |
-- >> normalizeMessage "Hello World" | |
-- "*hello *world" | |
normalizeMessage :: String -> String | |
normalizeMessage = | |
foldr f "" | |
where f c s = if isUpper c then | |
['*', toLower c] ++ s | |
else c:s | |
-- | Return keyIndex, charIndex for char | |
-- >>> pressFor defaultPad 'g' | |
-- Just (3,1) | |
-- >>> pressFor defaultPad 'z' | |
-- Just (8,4) | |
-- >>> pressFor defaultPad '%' | |
-- Nothing | |
-- >>> pressFor defaultPad '5' | |
-- Just (4,4) | |
pressFor :: Keypad -> Char -> Maybe (Int, Int) | |
pressFor (Keypad keys) c = | |
case findIndex (elem c) keys of | |
Nothing -> Nothing | |
Just keyIndex -> | |
let set = keys !! keyIndex | |
in case elemIndex c set of | |
Nothing -> Nothing | |
Just charIndex -> Just (keyIndex, charIndex + 1) | |
-- | Convert a key and presses to char | |
-- >>> pressesToKey defaultPad (3, 1) | |
-- 'd' | |
-- >>> pressesToKey defaultPad (9, 4) | |
-- 'z' | |
-- >>> pressesToKey defaultPad (5, 4) | |
-- '5' | |
pressesToKey :: Keypad -> (Int, Int) -> Char | |
pressesToKey (Keypad phone) (keyIndex, presses) = | |
let key = phone !! (keyIndex - 1) | |
in key !! (presses - 1 `mod` length key) | |
-- | Generate a sequence of keys to press | |
-- >>> seqForPress defaultPad (3, 1) | |
-- "4" | |
-- >>> seqForPress defaultPad (9, 4) | |
-- "****" | |
seqForPress :: Keypad -> (Int, Int) -> String | |
seqForPress (Keypad phone) (keyIndex, count) = | |
let keyStr = phone !! keyIndex | |
key = keyStr !! (length keyStr - 1) | |
ret = replicate count key | |
in ret | |
-- | Convert message to series of keypad presses | |
-- >>> convertKeypadMessage defaultPad "Hello World" | |
-- "**4433555555666**96667775553" | |
convertKeypadMessage :: Keypad -> String -> String | |
convertKeypadMessage phone msg = | |
concatMap (seqForPress phone) | |
(mapMaybe (pressFor phone) (normalizeMessage msg)) |
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