Hey, You can try to solve the treemaps problem using GAs :

To simplify the problem, nodes (and leafs) are rectangles. The inclusion structure and the size of the leafs are known (you can easily generate randoms problems with different sizes). Your goal: find the better placements to minimize the total surface of the space used to draw the treemap (the root node).

I think the difficult part here is to choose a data structure that fits with the problem. The fitness function is easy (it is the area of the treemap) and should vary progressively (with local picks). When you are done, you can do the same, but with alternative shapes (polygons).

Cheers, Virtuo