Problem:
Score : 300 points

Problem Statement

There is a grid with H rows and W columns, where each square is painted black or white.

You are given H strings S_1, S_2, ..., S_H, each of length W.
If the square at the i-th row from the top and the j-th column from the left is painted black, the j-th character in the string S_i is #; if that square is painted white, the j-th character in the string S_i is ..

Find the number of pairs of a black square c_1 and a white square c_2 that satisfy the following condition:

There is a path from the square c_1 to the square c_2 where we repeatedly move to a vertically or horizontally adjacent square through an alternating sequence of black and white squares: black, white, black, white...

Constraints

1 \leq H, W \leq 400

|S_i| = W (1 \leq i \leq H)

For each i (1 \leq i \leq H), the string S_i consists of characters # and ..

Input

Input is given from Standard Input in the following format:

H W
S_1
S_2
:
S_H

Output

Print the answer.

Sample Input 1

3 3
.#.
..#
#..

Sample Output 1

10

Some of the pairs satisfying the condition are ((1, 2), (3, 3)) and ((3, 1), (3, 2)), where (i, j) denotes the square at the i-th row from the top and the j-th column from the left.

Sample Input 2

2 4
....
....

Sample Output 2

0

Sample Input 3

4 3
###
###
...
###

Sample Output 3

6

Solution in Haskell (GHC 7.10.3) (judge verdict: Time Limit Exceeded)

import Control.Arrow
import Data.Foldable
import Data.Graph
import qualified Data.Vector as V
import qualified Data.ByteString.Char8 as B

solve :: Int -> Int -> V.Vector B.ByteString -> Int
solve h w ss = sum $ map ((\(x,y) -> x*y) . foldl' (\(b,w) i -> (if ss !! getNode i == '#' then first (+1) else second (+1)) (b,w)) (0,0)) $ components graph
  where
    toIndex :: Int -> (Int,Int)
    toIndex n = (n `mod` w, n `div` w)

    fromIndex :: (Int,Int) -> Int
    fromIndex (x,y) = y * w + x

    (!!) :: V.Vector B.ByteString -> (Int,Int) -> Char
    vec !! (x,y) = (vec V.! y) `B.index` x

    getNode = (\(_,i,_) -> i) . getNodeKey

    (graph, getNodeKey, getVertex) = graphFromEdges $ map (\i -> (toIndex i, toIndex i, neighbors $ toIndex i)) [0..w*h-1]
      where
        neighbors (x,y) =
          [(x',y') |
            (ix,iy) <- [(0,1),(0,-1),(1,0),(-1,0)],
            let x' = x + ix, let y' = y + iy,
            0 <= x' && x' < w, 0 <= y' && y' < h,
            ss !! (x',y') /= ss !! (x,y)
          ]

main = do
  let readInt = fmap (second B.tail) . B.readInt

  hw <- V.unfoldrN 2 readInt <$> B.getLine
  ss <- V.replicateM (hw V.! 0) B.getLine
  print $ solve (hw V.! 0) (hw V.! 1) ss