We consider the problem of finding all subtree repeats in a given unranked ordered tree. We show a new, elegant, and simple method, which is based on the construction of a tree indexing structure called the subtree pushdown automaton. We propose a solution for computing all subtree repeats from the deterministic subtree pushdown automaton constructed over the subject tree. The method we present...

We consider the graph center problem in the joinsemilattice L(T ) of all subtrees of a tree T . A subtree S of a tree T is a central subtree of T if S has the minimum eccentricity in the joinsemilattice. The graph center of the joinsemilattice is the set of all central subtrees. A central subtree with the minimum number of points is a least central subtree of a tree T . Thus least central subtr...

The maximum agreement subtree approach is one method of reconciling different evolutionary trees for the same set of species. An agreement subtree enables choosing a subset of the species for whom the restricted subtree is equivalent (under a suitable definition) in all given evolutionary trees. Recently, dynamic programming ideas were used to provide polynomial time algorithms for finding a ma...

String suffix automata accept all suffixes of a given string and belong to the fundamental stringology principles. Extending their transitions by specific pushdown operations results in new subtree pushdown automata, which accept all subtrees of a given subject tree in prefix notation and are analogous to the suffix automata in their properties. The deterministic subtree pushdown automaton acce...

In this paper, we study the enumeration problem for all induced subtrees in an input graph G. Although the subgraph version of the problem is known to be enumerable in output linear time, the induced version of the problem considered here has not been studied before and its complexity is not known so far. We first introduce the notion of the border of an induced subtree. Then, we present an enu...