Output-Polynomial Enumeration of All Fixed-Cardinality Ideals of a Poset, Respectively All Fixed-Cardinality Subtrees of a Tree
نویسنده
چکیده
The N cardinality k ideals of any w-element poset (w, k variable) can be enumerated in time O(Nw). The corresponding bound for k-element subtrees of a w-element tree is O(Nw).
منابع مشابه
An efficient data structure for counting all linear extensions of a poset, calculating its jump number, and the likes
Achieving the goals in the title (and others) relies on a cardinality-wise scanning of the ideals of the poset. Specifically, the relevant numbers attached to the k + 1 elment ideals are inferred from the corresponding numbers of the k-element (order) ideals. Crucial in all of this is a compressed representation (using wildcards) of the ideal lattice. The whole scheme invites distributed comput...
متن کاملAn FPT Variant Of The Shadow Problem With Kernelization
The shadow problem (SIS) gets as input a forest F , and a map that assigns subtrees, called shadows, to leaves of F . SIS asks whether there exists a set of |F | leaves, one from each tree, such that no leaf lies in the shadow of another. Usually SIS is considered as a parameterized problem with parameter k bounding the cardinality of F , for which some fixedparameter tractability time bounds h...
متن کاملOn Center Cycles in Grid Graphs
Finding “good” cycles in graphs is a problem of great interest in graph theory as well as in locational analysis. We show that the center and median problems are NP hard in general graphs. This result holds both for the variable cardinality case (i.e. all cycles of the graph are considered) and the fixed cardinality case (i.e. only cycles with a given cardinality p are feasible). Hence it is of...
متن کاملOn the fixed number of graphs
A set of vertices $S$ of a graph $G$ is called a fixing set of $G$, if only the trivial automorphism of $G$ fixes every vertex in $S$. The fixing number of a graph is the smallest cardinality of a fixing set. The fixed number of a graph $G$ is the minimum $k$, such that every $k$-set of vertices of $G$ is a fixing set of $G$. A graph $G$ is called a $k$-fixed graph, if its fix...
متن کاملBorel Ideals in Three Variables
i=1 gijXi, g = (gij) ∈ Gl(n,k)), given any term-ordering< and homogeneous ideal a ⊆ P(n), there exists a non-empty open subset U of Gl(n,k) such that as g ranges in U, gin(a) := in(g(a)) is constant. Moreover, gin(a) is fixed by the group B of upper-triangular invertible matrices, if X1 > · · · > Xn, while gin(a) is fixed by the group B′ of lower-triangular invertible matrices if X1 < · · · < X...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Order
دوره 31 شماره
صفحات -
تاریخ انتشار 2014