Published online by Cambridge University Press: 30 July 2009
This paper studies the computational complexity of the properinterval colored graph problem (PICG), when the input graphis a colored caterpillar, parameterized by hair length. In order prove ourresult we establish a close relationship between the PICG anda graph layout problem the proper colored layout problem(PCLP). We show a dichotomy: the PICG and thePCLP are NP-complete for colored caterpillars of hair length ≥2, while both problems are in P for colored caterpillarsof hair length <2.For the hardness results we provide a reduction from the multiprocessor scheduling problem, while the polynomial time resultsfollow from a characterization in terms of forbidden subgraphs.