Bounding restricted rotation distance

  • Authors:
  • Sean Cleary;Jennifer Taback

  • Affiliations:
  • Department of Mathematics, City College of CUNY, New York, NY;Department of Mathematics and Statistics, University at Albany, Albany, NY

  • Venue:
  • Information Processing Letters
  • Year:
  • 2003

Quantified Score

Hi-index 0.89

Visualization

Abstract

Restricted rotation distance between pairs of rooted binary trees quantifies differences in tree shape. Cleary exhibited a linear upper bound of 12n for the restricted rotation distance between two trees with n interior nodes, and a lower bound of (n - 1)/3 if the two trees satisfy a reduction condition. We obtain a significantly improved sharp upper bound of 4n - 8 for restricted rotation distance between two rooted binary trees with n interior nodes, and a significantly improved sharp lower bound of n - 2, again with the requirement that the trees satisfy a reduction condition. These improvements use work of Fordham to compute the word metric in Thompson's group F.