We consider the problem of searching in natural families of trees. A search in a tree T is a sequence of queries used to locate a pre-designated node called the \buggy" node. A query is made to any subtree in T. If the queried subtree contains the buggy node, then we restrict the search to that subtree, otherwise the search is restricted to the complement of that subtree in T. Two problems are ...

Let e be an edge of a median graph G which is contained in exactly one 4-cycle. Then it is proved that G n e is a median graph. The converse holds as well provided that e is not contained is a subgraph isomorphic to the 3-cube minus a vertex. These results are used to give several characterizations of median grid graphs. (Grid graphs are subgraphs of complete grids, i.e. of the Cartesian produc...

In this paper we present probabilistic algorithms over random binary search trees such that: a) the insertion of a set of keys in any xed order into an initially empty tree produces always a random tree; b) the deletion of any key of a random tree results in a random tree; c) the random choices made by the algorithms are based upon the sizes of the subtrees of the random tree, an information th...

The subtree transfer (STT) distance is one of the distance metric for comparing phylogenies. Previous work on computing the STT distance considered degree-3 trees only. In this paper, we give an approximation algorithm for the STT distance for degreed trees with arbitrary d and with generalized STT operations. Also, some NP-hardness results related to STT distance are presented.