Extending partial representations of proper and unit interval graphs

Pavel Klavík, Jan Kratochvíl, Yota Otachi, Ignaz Rutter, Toshiki Saitoh, Maria Saumell, Tomáš Vyskočil

Research output: Contribution to journalArticleAcademicpeer-review

25 Citations (Scopus)


The recently introduced problem of extending partial interval representations asks, for an interval graph with some intervals pre-drawn by the input, whether the partial representation can be extended to a representation of the entire graph. In this paper, we give a linear-time algorithm for extending proper interval representations and an almost quadratic-time algorithm for extending unit interval representations. We also introduce the more general problem of bounded representations of unit interval graphs, where the input constrains the positions of some intervals by lower and upper bounds. We show that this problem is NP-complete for disconnected input graphs and give a polynomial-time algorithm for the special class of instances, where the ordering of the connected components of the input graph along the real line is prescribed. This includes the case of partial representation extension. The hardness result sharply contrasts the recent polynomial-time algorithm for bounded representations of proper interval graphs (Balko et al. in 2013). So unless P=NP P=NP, proper and unit interval representations have vastly different structure. This explains why partial representation extension problems for these different types of representations require substantially different techniques.
Original languageEnglish
Pages (from-to)1071-1104
Number of pages34
Issue number4
Publication statusPublished - 1 Apr 2017


  • Intersection representation
  • Partial representation extension
  • Bounded representations
  • Restricted representation
  • Proper interval graph
  • Unit interval graph
  • Linear programming


Dive into the research topics of 'Extending partial representations of proper and unit interval graphs'. Together they form a unique fingerprint.

Cite this