On locally finite ordered rooted trees and their rooted subtrees

Abstract

In this article we compare the known dynamical polynomial time algorithm for the game-over attack strategy, to that of the brute force approach; of checking all the ordered rooted subtrees of a given tree that represents a given computer network. Our approach is purely enumerative and combinatorial in nature. We first revisit known results about a doubly exponential sequence and generalize them. We then consider both finite and locally finite ordered rooted trees (LFOR-trees), and the class of their finite ordered rooted subtrees of bounded height, describing completely the LFOR-trees with no leaves where the number of ordered rooted subtrees of height at most $h$ are bounded by a polynomial in $h$. We finally consider general LFOR-trees where each level can have leaves and determine conditions for the number of ordered rooted subtrees of height at most $h$ to be bounded by a polynomial in $h$.