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General Restricted Rotation Distance

Luccio, Fabrizio and Pagli, Linda (2004) General Restricted Rotation Distance. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.

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    The restricted rotation distance d_{R}(S,T) between two trees S, T of n vertices is the minimum number of rotations by which S can be transformed into T, where rotations can only take place at the root of the tree, or at the right child of the root. A sharp upper bound d_{R}(S,T)\leq 4n-8 is known, based on the word metric of Thompson's group. We refine this bound to d_{R}(S,T)\leq 4n-8-\rho_{S} \rho_{T}, where \rho_{S} and \rho_{T} are the numbers of vertices in the rightmost vertex chains of the two trees, providing a very simple transformation algorithm based on elementary properties of trees. We also generalize the concept of restricted rotation by allowing rotations at the highest k levels of the tree, and study the new distance for k=2,3.

    Item Type: Book
    Uncontrolled Keywords: Rotation distance, Binary trees, Search
    Subjects: Area01 - Scienze matematiche e informatiche > INF/01 - Informatica
    Divisions: Dipartimenti (until 2012) > DIPARTIMENTO DI INFORMATICA
    Depositing User: dott.ssa Sandra Faita
    Date Deposited: 09 Dec 2014 11:01
    Last Modified: 09 Dec 2014 11:01
    URI: http://eprints.adm.unipi.it/id/eprint/2127

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