Sheila Morais Almeida

Sheila Morais Almeida
Federal University of Technology - Paraná/Brazil (UTFPR) | UTFPR · Academic Department of Informatics

Professor

About

29
Publications
1,687
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
26
Citations
Introduction
I am a graph theorist, currently interested in graph coloring problems. My research is mainly dedicated to the search for polynomial-time algorithms for NP-complete problems when restricted to specific graph classes.
Additional affiliations
November 2012 - January 2021
Federal University of Technology - Paraná/Brazil (UTFPR)
Position
  • Professor (Full)
Description
  • I'm a Professor of the Academic Department of Informatics and the Computer Science Graduate Program. I have taught classes on discrete mathematics, graph theory, and algorithm analisys. I advise undergraduate and graduate students working on Graph Theory and Computational Complexity topics. I'm currently working on designing polynomial-time algorithms to the Edge-Coloring and Total-Coloring problems in subclasses of perfect graphs.
September 2009 - November 2012
Universidade Federal de Mato Grosso do Sul
Position
  • Professor (Full)
Description
  • Professor of discrete mathematics, graph theory, data structure, computational complexity, algorithm analysis, formal language, and automata.
Education
April 2005 - March 2012
University of Campinas
Field of study
  • Computing
March 2003 - April 2005
University of Campinas
Field of study
  • Computing
March 1999 - December 2002
University of Campinas
Field of study
  • Computing

Publications

Publications (29)
Article
Rainbow coloring problems, of noteworthy applications in Information Security, have been receiving much attention in the last years in Combinatorics. In particular, the rainbow connection number of a connected graph G, denoted rc(G), is the least k for which G admits a (not necessarily proper) k-edge-coloring such that between any pair of vertices...
Article
The chromatic index of a graph G, χ'(G), is the least number of colors of some edge coloring of G such that no two adjacent edges have the same color. Given a graph G and an integer k, to decide if χ'(G) ≤ k is NP-complete. A graph is an interval graph if it represents the intersection relation of a set of closed intervals in R. A graph is a split...
Conference Paper
Rainbow coloring problems, of noteworthy applications in Information Security, have been receiving much attention last years in Combinatorics. The rainbow connection number of a graph G is the least number of colors for a (not necessarily proper) edge coloring of G such that between any pair of vertices there is a path whose edge colors are all dis...
Conference Paper
Full-text available
A rainbow coloring of a connected graph 𝐺 is an edge coloring that is not necessarily proper such that there is a path between any pair of vertices of 𝐺 whose edge colors are pairwise distinct. The rainbow connection number of a graph 𝐺, denoted by 𝑟𝑐(𝐺), is the least number of colors for which there is a rainbow coloring of 𝐺. A graph 𝐺 is rainbow...
Article
Full-text available
Consider a vertex coloring of a graph where each color is represented by a natural number. The color sum of a vertex is the sum of the colors of its adjacent vertices. The Sigma Coloring Problem concerns determining the sigma chromatic number of a graph G, σ(G), which is the least number of colors for a coloring of G such that the color sum of any...
Article
In a proper edge coloring of a graph, the set of colors of a vertex v is the set of colors of the edges incident to v, C(v). If C(u)≠C(v) for every adjacent vertices u and v, this edge coloring is an AVD-edge coloring. The least number of colors for which G has an AVD-edge coloring is called the AVD-chromatic index, χa′(G). We determine the AVD-chr...
Article
We show in this paper that a split-comparability graph $G$ has chromatic index equal to $\Delta(G) + 1$ if and only if $G$ is neighborhood-overfull. That implies the validity of the Overfull Conjecture for the class of split-comparability graphs.
Conference Paper
Full-text available
Given a graph G, an edge-coloring of G is an assingment of colors to the edges of G. A proper edge-coloring is an edge coloring if adjacent edges have different colors. A rainbow coloring of a connected graph G is an edge coloring that is not necessarily proper such that there is a path between any pair of vertices of G whose edge colors are pairwi...
Conference Paper
The rainbow connection number of a connected graph G, denoted by rc(G), is the minimum number of colors needed to color the edges of G, so that every pair of vertices is connected by at least one path in which the colors of the edges are pairwise distinct. In this work we determine the rainbow connection number for the graphs Cm × Pn when m is odd...
Conference Paper
Full-text available
Let F be a family of sets. The diversity of F, Υ(F), is the amount of different cardinalities on the sets of F. The class of graphs whose diversity of the maximal independent set equals Υ(F) is denoted by M(Υ(F)). Recognizing the M(t) class for a given t is a Co-NP-complete problem. However, it is possible to recognize the M(1) graphs and the simpl...
Conference Paper
Full-text available
O Problema da Coloração de Arestas Distinta nos Vértices Adjacentes consiste em, dado um grafo, utilizar o menor número de cores possível para colorir suas arestas de forma que arestas incidentes no mesmo vértice tenham cores distintas e o conjunto de cores incidentes em cada vértice seja diferente dos conjuntos de cores dos seus vizinhos. Nesse tr...
Conference Paper
Full-text available
The Minimum Dominating Set Problem is to find the least vertex set D such that every vertex belongs to D or is adjacent to a vertex in D. It is known that the Minimum Dominating Set Problem is NP-complete. In this work we investigate the Minimum Dominating Set Problem on lexico-graphic product of graphs. Due to a famous conjecture of V. G. Vinzing,...
Article
Along with a result of Niessen of 1994, a conjecture proposed by Hilton and Chetwynd of 1986 implies that the chromatic index of graphs with can be determined in linear time. Connected cographs satisfy , however whether the conjecture holds for cographs is still unknown. This paper presents sufficient conditions for cographs and join graphs to be C...
Article
Full-text available
The Classification Problem is the problem of deciding whether a simple graph has chromatic index equal to Δ or Δ+1. In the first case, the graphs are called Class 1, otherwise, they are Class 2. A split graph is a graph whose vertex set admits a partition into a stable set and a clique. Split graphs are a subclass of chordal graphs. Figueiredo at a...
Article
Full-text available
The classification problem is the problem of deciding whether a simple graph has chromatic index equal to Δ or Δ+1. In the first case, the graphs are called Class 1, otherwise, they are Class 2. A split graph is a graph whose vertex set admits a partition into a stable set and a clique. Split graphs are a subclass of chordal graphs. C. M. H. de Fig...
Article
The Classification Problem is the problem of deciding whether a simple graph has chromatic index equals to Δ or Δ + 1, where Δ is the maximum degree of the graph. It is known that to decide if a graph has chromatic index equals to Δ is NP-complete. A split graph is a graph whose vertex set admits a partition into a stable set and a clique. The chro...
Article
Full-text available
The Classification Problem is the problem of deciding whether a simple graph has chromatic index equals to Delta or Delta + 1, where Delta is the maximum degree of the graph. It is known that to decide if a graph has chromatic index equals to Delta is NP-complete. A split graph is a graph whose vertex set admits a partition into a stable set and a...
Article
Full-text available
Consider two parallel lines (denoted by r1 and r2). A graph is a PI graph (Point-Interval graph) if it is an intersection graph of a family F of triangles between r1 and r2such that each triangle has an interval with two endpoints on r1 and a vertex (a point)on r2. The family F is the PI representation of G. The PI graphs are an extension ofinterva...
Article
We describe an ongoing project whose aim is to build a parser for Brazilian Portuguese, Selva, which can be used as a basis for subsequent research in natural language processing, such as automatic translation and ellipsis and anaphora resolution. The parser is meant to handle arbitrary prose texts in unrestricted domains, including the full range...
Conference Paper
We describe an ongoing project whose aim is to build a parser for Brazilian Portuguese, Selva, which can be used as a basis for subsequent research in natural language processing, such as automatic translation and ellipsis and anaphora resolution. The parser is meant to handle arbitrary prose texts in unrestricted domains, including the full range...

Projects

Projects (2)
Project
This project investigates the Edge Coloring Problem, the Total Coloring Problem, and other correlated graph coloring problems. The decision versions of these problems are NP-complete. As with all the NP-complete problems, to develop an efficient algorithm to solve the problem for the general case proves P = NP, a result with a significant impact on the computing field. If such an algorithm does not exist, then it remains to develop efficient algorithms for the NP-complete problems restricted to specific cases with instances that meet well-defined constraints. The decision version of the Edge Coloring Problem restricted to the comparability graphs is NP-complete. However, interval graphs with an odd maximum degree and split graphs with an odd maximum degree are comparability graphs and have polynomial-time algorithms that solve this problem. The decision version of the Total Coloring Problem is NP-Complete even when restricted to bipartite graphs. However, there are efficient algorithms to determine the total chromatic number for complete bipartite graphs, grids, and trees. For both problems, we intend to investigate for which other subsets of graphs there are polynomial-time algorithms.