Title
On extensions, linear extensions, upsets and downsets of ordered sets
Abstract
We consider the problem of characterizing the set @e(P) of all extensions of an order P on a set of elements E, where |E|=n, |P|=m and @m is the number of extensions of the order. Initially, we describe two distinct characterizations of @e(P). The first characterization is a one-to-one correspondence between extensions of P and pairs of upsets and downsets of certain suborders of P. The second one characterizes the extensions of P in terms of linear extensions and sequences of downsets. Both characterizations lead to algorithms that generate all the extensions of P. Further, we discuss the notion of passive pairs of an order. Based on it, we describe a third characterization of @e(P) and an algorithm that generates all the extensions of P in O(n) amortized time per extension.
Year
DOI
Venue
2005
10.1016/j.disc.2004.12.007
Discrete Mathematics
Keywords
Field
DocType
extensions,enumeration,ordered sets,linear extension
Discrete mathematics,Ordered set,Combinatorics,Enumeration,Amortized analysis,Mathematics
Journal
Volume
Issue
ISSN
295
1-3
Discrete Mathematics
Citations 
PageRank 
References 
1
0.36
7
Authors
2
Name
Order
Citations
PageRank
Ricardo C. Corrêa120718.74
Jayme L. Szwarcfiter254645.97