Lake Counting(POJ No.2386)

lake_counting.rb

## Lake Counting(POJ No.2386)
## http://rubyfiddle.com/riddles/2f66f

N = 10
M = 12

$field = []

#庭の状態
data = <<"EOS"
w........ww.
.www.....www
....ww...ww.
.........ww.
.........w..
..w......w..
.w.w.....ww.
w.w.w.....w.
.w.w......w.
..w.......w.
EOS

data = data.split("\n")

data.size.times{|i|
  $field[i] = data[i].split("")
}

def dfs(x,y)
 $field[x][y]= "."
  -1.upto(1){|dx|
    -1.upto(1){|dy|
      nx = x + dx
      ny = y + dy
      if(0<=nx && nx<N && 0<=ny && ny<M && $field[nx][ny]=="w")
        dfs(nx,ny)
      end
    }
  }
end
  
res = 0

N.times{|i|
 M.times{|j|
    if $field[i][j] == "w"
      dfs(i,j)
      res += 1
    end
 }
}

puts res