Problem.A.hs

import Data.List
import Data.Char
import Control.Monad
-- transpose
input="A-small-practice.in"

data Result = WinX | WinO | Draw | DontKnow deriving (Show, Eq)
type Board = [String]
whoWin :: Board -> Result
whoWin b 
 | isXwin $ possibleSeq b = WinX
 | isOwin $ possibleSeq b = WinO
 | hasEmpty b = DontKnow
 | otherwise = Draw
 
isXwin xs = or [isWin 'X' seq | seq <- xs]
isOwin xs = or [isWin 'O' seq | seq <- xs]
isWin who seq = and [ch == who || ch == 'T' | ch <- seq]
hasEmpty b = or [ ch == '.' | ch <- foldl (++) "" b ]

possibleSeq b = b++transpose b++[crossDown b]++[crossUp b]
-- (0,0):(1,1):(2,2):(3,3)
crossDown b = (b !! 0 !! 0):(b !! 1 !! 1):(b !! 2 !! 2):(b !! 3 !! 3):[]
-- (0,3):(1,2):(2,1):(3,0)
crossUp b = (b !! 0 !! 3):(b !! 1 !! 2):(b !! 2 !! 1):(b !! 3 !! 0):[]

main = do
  s <- readFile input
  let isNumberStr xs = and [isDigit x | x <- xs]
  let flattenBoards = let (head:xs) = filter (/= "") (lines s) in
                      if isNumberStr head then xs else (head:xs)
  let boards = toBoards flattenBoards
  zipWithM_ (\count board -> print (judge count board)) [1..] boards

toBoards [] = []
toBoards flattenBoards = [take 4 flattenBoards] ++ (toBoards $ drop 4 flattenBoards)

judge count board = 
  let r = case whoWin board of
           WinX -> "X won"
           WinO -> "O won"
           Draw  -> "Draw"
           DontKnow -> "Game has not completed"
  in "Case #" ++ show count ++ ": " ++ r