FPT Algorithms for Crossing Number Problems: A Unified Approach

The basic crossing number problem is to determine the minimum number of crossings in a topological drawing of an input graph in the plane. In this paper, we develop fixed-parameter tractable (FPT) algorithms for various generalized crossing number problems in the plane or on surfaces. Our first result is on the color-constrained crossing problem, in which edges of the input graph G are colored, and one looks for a drawing of G in the plane or on a given surface in which the total number of crossings involving edges of colors i and j does not exceed a given upper bound Mij. We give an algorithm for this problem that is FPT in the total number of crossings allowed and the genus of the surface. It readily implies an FPT algorithm for the joint crossing number problem. We also give new FPT algorithms for several other graph drawing problems, such as the skewness, the edge crossing number, the splitting number, the gap-planar crossing number, and their generalizations to surfaces. Our algorithms are reductions to the embeddability of a graph on a two-dimensional simplicial complex, which admits an FPT algorithm by a result of Colin de Verdi\`ere and Magnard [ESA 2021].