Maximum cuts in edge-colored graphs

The input of the Maximum Colored Cut problem consists of a graph G = (V, E) with an edge-coloring c : E -> {1, 2, 3,..., p} and a positive integer k, and the question is whether G has a nontrivial edge cut using at least k colors. The Colorful Cut problem has the same input but asks for a nontrivial edge cut using all p colors. Unlike what happens for the classical Maximum Cut problem, we prove that both problems are NP-complete even on complete, planar, or bounded treewidth graphs. Furthermore, we prove that Colorful Cut is NP-complete even when each color class induces a clique of size at most three, but is trivially solvable when each color induces an edge. On the positive side, we prove that Maximum Colored Cut is fixed-parameter tractable when parameterized by either k or p, by constructing a cubic kernel in both cases. (c) 2019 Elsevier B.V. All rights reserved.