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 kernalization of the initial trees to trees with size bounded by 7k.
Recently it was proved that the problem is fixed parameter tractable in the flip distance REF .
Rotation Distance is Fixed-Parameter Tractable
Inform. Process. Lett. 109 (2009), no. 16, 918-922
Mathematics Computer Science