/
LakeCounting.hs
43 lines (34 loc) · 1000 Bytes
/
LakeCounting.hs
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import Control.Monad
import Data.IORef
import Data.Foldable(foldlM)
(n,m) = (10,12)
field = ["W........WW."
,".WWW.....WWW"
,"....WW...WW."
,".........WW."
,".........W.."
,"..W......W.."
,".W.W.....WW."
,"W.W.W.....W."
,".W.W......W."
,"..W.......W."
]
value (x,y) = (field !! x) !! y
inField (x,y)
= 0<=x && x<n && 0<=y && y<m
dfs p visitedRef = do
modifyIORef visitedRef (p:)
forM_ (near4pos p) $ \p' ->
when (value p' == 'W') $ dfs p' visitedRef
near4pos (x,y) = filter inField [ {-(x,y)-}( x ,y+1),
(x+1,y-1),(x+1,y),(x+1,y+1)]
solve (c,visitedRef) p = do
visited <- readIORef visitedRef
if value p == 'W' && all (/=p) visited --未訪問且つ池
then dfs p visitedRef
>> return (c+1,visitedRef)
else return (c,visitedRef)
main = do
visitedRef <- newIORef []
print.fst =<< foldlM solve (0,visitedRef)
[(x,y)| x<-[0..n-1] , y<-[0..m-1] ]