[de90]

Why? All you need to know is the grid width\height, and whether a grid coord is empty. All of which is shown in the example.

[karcass]

My solution required marking each coord as non-empty when I dropped a rect on it. I was able to hack something that worked (non-zero-len string stuffed into the structure), but I'd much rather know what the structure was instead of guessing.

p.s. 29 ha ha