SPLIT
Implementation of the Split algorithm. It is described in:
Engdahl, B. "Ordered and Unordered Treemap Algorithms and Their Applications on Handheld Devices". 2005.
Produces a layout where the natural ordering of the data set is roughly preserved, while in most cases producing better aspect ratios than the Pivot and the Strip treemaps.
Complexity: O(n log n) (worst case), O(n) average, where n is the number of nodes in the tree.