Rotation distance is fixed-parameter tractable
Rotation distance between trees measures the number of simple operations it takes to transform one tree into another. There are no known polynomial-time algorithms for computing rotation distance. In the case of ordered rooted trees, we show that the rotation distance between two ordered trees is fixed-parameter tractable, in the parameter, k, the rotation distance. The proof relies on the kernelization of the initial trees to trees with size bounded by 5k. (C) 2009 Published by Elsevier B.V.
rotation distance analysis of algorithms computational complexity fixed parameter tractability