Abstract
This paper presents efficient exponential time algorithms for the unordered tree edit distance problem, which is known to be NP-hard. For a general case, an \(O(1.26^{n_1+n_2})\) time algorithm is presented, where n 1 and n 2 are the numbers of nodes in two input trees. This algorithm is obtained by a combination of dynamic programming, exhaustive search, and maximum weighted bipartite matching. For bounded degree trees over a fixed alphabet, it is shown that the problem can be solved in \(O((1+\epsilon)^{n_1+n_2})\) time for any fixed ε > 0. This result is achieved by avoiding duplicate calculations for identical subsets of small subtrees.Keywordstree edit distanceunordered treesdynamic programmingmaximum weight bipartite matching
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