A metric between unrooted and unordered trees and its bottom-up computing method

Proposes a distance measure between unrooted and unordered trees based on the strongly structure-preserving mapping (SSPM). SSPM can make correspondences between the vertices of similar substructures of given structures more strictly than previously proposed mappings. The time complexity of computing the distance between trees T/sub a/ and T/sub b/ is O(m/sub bsup 3/N/sub a/N/sub b/), where N/sub a/ and N/sub b/ are the number of vertices in trees T/sub a/ and T/sub b/, respectively; m/sub a/ and m/sub b/ are the maximum degrees of a vertex in T/sub a/ and T/sub b/, respectively; and m/sub aspl les/m/sub b/ is assumed. The space complexity of the method is O(N/sub a/N/sub b/).<
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