Hi.
if its grid based, maybe make an array or some array where you store the positions of what have been placed.
Then you can loop thru the list and do for example a distance compare
or for example if you grid is for example 5x10, have 5 arrays (int) and sized 10
Then if you place something in the top left then set a int in the 1st array on index 0
The int can be any value which can help to know what is placed.
if 0 the spot is empty.
Probably best to use array makers array lists (you can set a reference on the array : 0,1,2,3,4 for the rows)