Utilitas Algorithmica (UA)
ISSN: xxxx-xxxx (print)
Utilitas Algorithmica (UA) is a premier, open-access international journal dedicated to advancing algorithmic research and its applications. Launched to drive innovation in computer science, UA publishes high-impact theoretical and experimental papers addressing real-world computational challenges. The journal underscores the vital role of efficient algorithm design in navigating the growing complexity of modern applications. Spanning domains such as parallel computing, computational geometry, artificial intelligence, and data structures, UA is a leading venue for groundbreaking algorithmic studies.
- Research article
- Full Text
- Ars Combinatoria
- Volume 094
- Pages: 61-64
- Published: 31/01/2010
A construction of optimal quaternary codes from symmetrical Balanced Incomplete Block (BIB) design \((4t – 1, 2t – 1, t – 1)\) is described.
- Research article
- Full Text
- Ars Combinatoria
- Volume 094
- Pages: 55-59
- Published: 31/01/2010
For integers \(s,t \geq 1\), the Ramsey number \(R(s, t)\) is defined to be the least positive integer \(n\) such that every graph on \(n\) vertices contains either a clique of order \(s\) or an independent set of order \(t\). In this note, we derive new lower bounds for the Ramsey numbers: \(R(6,8) \geq 129\), \(R(7,9) \geq 235\) and \(R(8,17) \geq 937\). The new bounds are obtained with a constructive method proposed by Xu and Xie et al. and the help of computer algorithm.
- Research article
- Full Text
- Ars Combinatoria
- Volume 094
- Pages: 33-53
- Published: 31/01/2010
We pursue the problem of counting the imbeddings of a graph in each of the orientable surfaces. We demonstrate how to achieve this for an iterated amalgamation of arbitrarily many copies of any graph whose genus distribution is known and further analyzed into a partitioned genus distribution. We introduce the concept of recombinant strands of face-boundary walks, and we develop the use of multiple production rules for deriving simultaneous recurrences. These two ideas are central to a broad-based approach to calculating genus distributions for graphs synthesized from smaller graphs.
- Research article
- Full Text
- Ars Combinatoria
- Volume 094
- Pages: 25-32
- Published: 31/01/2010
The super (resp., edge-) connectivity of a connected graph is the minimum cardinality of a vertex-cut (resp., an edge-cut) whose removal does not isolate a vertex. In this paper, we consider the two parameters for a special class of graphs \(G(G_p,G_1; M)\), proposed by Chen et al [Applied Math. and Computation, \(140 (2003), 245-254]\), obtained from two \(k\)-regular \(k\)-connected graphs \(G_p\) and \(G_1\), with the same order by adding a perfect matching between their vertices. Our results improve ones of Chen et al. As applications, the super connectivity and the super edge-connectivity of the \(n\)-dimensional hypercube, twisted cube, cross cube, Möbius cube and locally twisted cube are all \(2n – 2\).
- Research article
- Full Text
- Ars Combinatoria
- Volume 094
- Pages: 3-11
- Published: 31/01/2010
We investigate the existence of \(3\)-designs and uniform large sets of \(3\)-designs with block size \(6\) admitting \(\text{PSL}(2, 2^n)\) as an automorphism group.
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 071
- Pages: 283-293
- Published: 28/02/2009
A simple graph \( G = (V(G), E(G)) \) admits an \( H \)-covering if every edge in \( E(G) \) belongs to a subgraph of \( G \) that is isomorphic to \( H \). An \((a,d)\)-\( H \)-\({antimagic\; total \;labeling}\) of \( G \) is a bijective function \( \xi : V(G) \cup E(G) \to \{1,2,\dots,|V(G)| + |E(G)|\} \) such that for all subgraphs \( H’ \) isomorphic to \( H \), the \( H \)-weights \( w(H’) = \sum_{v \in V(H’)} \xi(v) + \sum_{e \in E(H’)} \xi(e) \) constitute an arithmetic progression \( a, a+d, a+2d, \dots, a+(t-1)d \), where \( a \) and \( d \) are positive integers and \( t \) is the number of subgraphs of \( G \) isomorphic to \( H \). Additionally, the labeling \( \xi \) is called a \({super}\) \((a, d)\)-\( H \)-\({antimagic\; total\; labeling}\) if \( \xi(V(G)) = \{1, 2, \dots, |V(G)|\} \).
In this paper, we introduce the notion of \((a, d)\)-\( H \)-\({antimagic\; total\; labeling}\) and study some basic properties of such labeling. We provide an example of a family of graphs obtaining the labelings, that is providing \((a, d)\)-cycle-antimagic labelings of fans.
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 071
- Pages: 273-281
- Published: 28/02/2009
Let \( j \geq 2 \) be a natural number. For graphs \( G \) and \( H \), the size multipartite Ramsey number \( m_j(G, H) \) is the smallest natural number \( t \) such that any \( 2 \)-coloring by red and blue on the edges of \( K_{j \times t} \) necessarily forces a red \( G \) or a blue \( H \) as a subgraph. Let \( P_n \) be a path on \( n \) vertices. In this note, we determine the exact value of the size multipartite Ramsey number \( m_j(P_4, P_n) \) for \( n \geq 2 \).
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 071
- Pages: 265-271
- Published: 30/11/2009
Let \(j \geq 2\) be a natural number. For graphs \(G\) and \(H\), the size multipartite Ramsey number \(m_j(G, H)\) is the smallest natural number \(t\) such that any \(2\)-coloring by red and blue on the edges of \(K_{j \times t}\) necessarily forces a red \(G\) or a blue \(H\) as subgraph. Let \(P_n\) be a path on \(n\) vertices. In this note, we determine the exact value of the size multipartite Ramsey number \(m_j(P_4, P_n)\) for \(n \geq 2\).
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 071
- Pages: 257-264
- Published: 30/11/2009
In this paper, we determine the Ramsey number for the disjoint union of graphs versus a graph \( H \), especially \( R\left(\bigcup_{i=1}^{k} l_i S_{n_i}(1,1), W_6\right) \), \( R\left(\bigcup_{i=1}^{k} l_i S_{n_i}(1,2), W_6\right) \), and \( R\left(\bigcup_{i=1}^k l_i S_{n_i}, W_4\right) \).
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 071
- Pages: 243-256
- Published: 30/11/2009
In this paper, we discuss an upper bound for exponents of loopless asymmetric two-colored digraphs. If \( D \) is an asymmetric primitive two-colored digraph on \( n \) vertices, we show that \( \text{exp}(D) \leq 3n^2 + 2n – 2 \). For an asymmetric two-colored digraph \( D \) which contains a primitive two-colored cycle of length \( s \leq n \), we show its exponent is at most \( \frac{s^2 – 1}{2} + (s + 1)(n – s) \). We characterize such two-colored digraphs whose exponents equal \( \frac{s^2 – 1}{2} + (s + 1)(n – s) \) and show that the largest exponent of an asymmetric two-colored digraph lies in the interval \( \left[\frac{n^2 – 1}{2}, 3n^2 + 2n – 2\right] \) when \( n \) is odd, or \( \left[\frac{n^2}{2}, 3n^2 + 2n – 2\right] \) otherwise.




