Google Code Jam 2016 Qualification Round : Problem B. Revenge of the Pancakes

b.hs

import Debug.Trace

testloop :: Integer -> Integer -> IO String 
testloop i t | i>t = return ""
testloop i t = getLine >>= testnum 0 >>= \x->return ("Case #"++(show i)++": "++x) >>= putStrLn >> testloop (i+1) t

testnum :: Integer -> String -> IO String
--testnum n s = flipcakes s >>= \x-> trace(x) (oneside n x)
testnum n s = case oneside n s of
	Just n | any (=='+') s == True -> return $ show n
	Just n -> return $ show $ n+1
	Nothing -> flipcakes s >>= testnum (n+1)

flipcakes :: String -> IO String
flipcakes s@(x:xs) = return $ (flipcake $ reverse $ takeWhile(==x) s) ++ (dropWhile(==x) s)

oneside :: Integer -> String -> Maybe Integer
oneside n (x:xs) | all (==x) xs == True = return n
oneside n (x:xs) = Nothing

flipcake :: String -> String
flipcake (x:xs) = y:ys
	where
		y = case x of
			'+' -> '-'
			'-' -> '+'
		ys = flipcake xs
flipcake [] = []

main = getLine >>= \t-> testloop 1 $ read t