Title
Enumeration of subtrees and BC-subtrees with maximum degree no more than k in trees
Abstract
The subtrees and BC-subtrees (subtrees where any two leaves are at even distance apart) have been intensively studied in recent years. Such structures, under special constraints on degrees, have a wide range of applications in many fields. By way of an approach based on generating functions, we present novel recursive algorithms for enumerating various subtrees and BC-subtrees of maximum degree <= k in trees. The algorithms are explained through detailed examples. We also briefly discuss, in trees, the densities of subtrees (resp. BC-subtrees) with maximum degree <= k among all subtrees (resp. BC-subtrees). For a tree of order n, the novelly proposed algorithms have multiple advantages. (1) Novel (k + 2) (resp. (2k + 3)) variable generating functions were introduced to construct the algorithms. (2) The proposed algorithms solved the fast enumerating problem of subtree (resp. BC-subtrees) with maximum degree constraint, and also make the subtree (resp. BC-subtrees) enumerating algorithms proposed by Yan and Yeh [1] (resp. Yang et al. [2]) a special case of ours with k = n - 1. (3) The time complexity of our algorithm for subtree (resp. BC-subtrees) is O (kn) (resp. O(kn(2))), which is much faster than the O(n2) (resp. O(kn(3))) time method based on algorithm proposed in [1] (resp. [2]). (c) 2021 Elsevier B.V. All rights reserved.
Year
DOI
Venue
2021
10.1016/j.tcs.2021.09.024
THEORETICAL COMPUTER SCIENCE
Keywords
DocType
Volume
Subtree, BC-subtree, Maximum degree, Generating function
Journal
892
ISSN
Citations 
PageRank 
0304-3975
0
0.34
References 
Authors
0
6
Name
Order
Citations
PageRank
Yu Yang1183.42
Xiao-xiao Li200.34
Meng-yuan Jin300.34
Long Li400.34
Hua Wang55811.74
Xiao-Dong Zhang6197.31