Graph editing problems have a long history and have been widely studied [35, 53] , with applications in biochemistry [23] and complex network analysis [5]. They generally ask whether an input graph can be modified by inserting and deleting vertices and edges to a graph with the desired property [5, 22]. We consider the problem Graph-Editto-NDL (GEN) where the goal is to modify to a graph with a...

We consider new parameterizations of NP-optimization problems that have nontrivial lower and/or upper bounds on their optimum solution size. The natural parameter, we argue, is the quantity above the lower bound or below the upper bound. We show that for every problem in MAX SNP, the optimum value is bounded below by an unbounded function of the input-size, and that the above-guarantee paramete...

We investigate the parameterized complexity of strategic behaviors in generalized scoring rules. In particular, we prove that the manipulation, control (all the 22 standard types), and bribery problems are fixed-parameter tractable for most of the generalized scoring rules, with respect to the number of candidates. Our results imply that all these strategic voting problems are fixed-parameter t...

We prove that the Graph Isomorphism problem is fixed-parameter tractable when parameterized by the feedback vertex set number. That parameter is defined as the number of vertex deletions required to obtain a forest. For graphs of bounded feedback vertex set number the presented algorithm runs in time O(n), and is thereby the first fixed-parameter tractable Graph Isomorphism algorithm for a non-...

It has recently been shown that the NP-hard problem of calculating the minimum number of hybridization events that is needed to explain a set of rooted binary phylogenetic trees by means of a hybridization network is fixed-parameter tractable if an instance of the problem consists of precisely two such trees. In this paper, we show that this problem remains fixed-parameter tractable for an arbi...

We consider the following problem called the k-Chinese Postman Problem (k-CPP): given a connected edge-weighted graph G and integers p and k, decide whether there are at least k closed walks such that every edge of G is contained in at least one of them and the total weight of the edges in the walks is at most p? The problem k-CPP is NP-complete, and van Bevern et al. (to appear) and Sorge (201...

Fixed-parameter intractability of optimization problems in NP is studied based on computational models with limited nondeterminism. Strong evidence is provided that many NP optimization problems are not fixed-parameter tractable and that the fixed-parameter intractability hierarchy (the W -hierarchy) does not collapse.

We extend the notion of a strong backdoor from the CSP setting to the Valued CSP setting (VCSP, for short). This provides a means for augmenting a class of tractable VCSP instances to instances that are outside the class but of small distance to the class, where the distance is measured in terms of the size of a smallest backdoor. We establish that VCSP is fixed-parameter tractable when paramet...