@techreport{TR-IC-14-12, number = {IC-14-1208-45}, author = {Cleber {Mira} and João {Meidanis}}, title = {{Sorting by Fissions, Fusions, and Signed Reversals in $O(n)$}}, month = {August}, year = {2014}, institution = {Institute of Computing, University of Campinas}, note = {In English, 20 pages. \par\selectlanguage{english}\textbf{Abstract} Measuring the minimum number of rearrangement events that transforms a genome into another is an important tool for the comparative analysis of genomes. We propose a new algorithm for finding a minimum sequence of Fissions, Fusions, and Signed Reversals that transforms a genome into another. The algorithm is based on representing a chromosome as a cycle (a circular sequence) instead of a mapping. Thus a genome is a product of cycles instead of the usual representation as a set of mappings. By representing a chromosome as a cycle, rearrangement events like fissions, fusions, and signed reversals are performed in constant running time. Besides the change in the representation, the algorithm uses a hash table to deal with the problem of using the gene names for indexes. The total time complexity is $O(nh)$, where $n$ is the number of genes and $h$ is the time spent to retrieve data for a gene in the hash table (ideally $h$ is a constant). We also present a formula for the minimum number of Fissions, Fusions, and Signed Reversals that can be calculated in $O(nh)$ running time. } }