Fixed-Parameter Complexity of Minimum Profile Problems
Let G=(V,E) be a graph. An ordering of G is a bijection α:V\dom{1,2,...,∣V∣}. For a vertex v in G, its closed neighborhood is N[v]={u∈V:uv∈E}∪{v}. The profile of an ordering α of G is \prfα(G)=∑v∈V(α(v)−min{α(u):u∈N[v]}). The profile \prf(G) of G is the minimum of \prfα(G) over all orderings α of G. It is well-known that \prf(G) is the minimum number of edges in an interval graph H that contains G is a subgraph. Since ∣V∣−1 is a tight lower bound for the profile of connected graphs G=(V,E), the parametrization above the guaranteed value ∣V∣−1 is of particular interest. We show that deciding whether the profile of a connected graph G=(V,E) is at most ∣V∣−1+k is fixed-parameter tractable with respect to the parameter k. We achieve this result by reduction to a problem kernel of linear size.