This paper presents two sets of techniques for comparing unrooted evolutionary trees, namely, label compression and four-way dynamic programming. The technique of four-way dynamic programming transforms existing algorithms for computing rooted maximum agreement subtrees into new ones for unrooted trees. Let n be the size of the two input trees. This technique leads to an O(n log n)-time algorithm for unrooted trees whose degrees are bounded by a constant, matching the best known complexity for the rooted binary case. The technique of label compression is not based on dynamic programming. With this technique, we obtain an O(n1.5 log n)-time algorithm for unrooted trees with arbitrary degrees, also matching the best algorithm for the rooted unbounded degree case.
|Original language||English (US)|
|Number of pages||12|
|Journal||Conference Proceedings of the Annual ACM Symposium on Theory of Computing|
|State||Published - Jan 1 1997|
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