Anyone knows an algorithm for finding “shapes” in 2d arrays?

Question

Let\'s take this map, where \'#\' illustrates a taken square and \'.\' illustrates a free square:

1 . # # # . .
2 . # . . # .
3 # . . . . #
4 . # # # . .
5 . . . . .          


        

Answer 1

I think this question can be reduced to a convex hull problem if we consider each # as point x,y then convex hull be give us the x,y of all the # which are absent

http://en.wikipedia.org/wiki/Convex_hull

I will try to code it in leisure ..