On the complexity of finding iso- and other morphisms for partial k-trees
Discrete Mathematics - Topological, algebraical and combinatorial structures; Froli´k's memorial volume
Graph minors. XIII: the disjoint paths problem
Journal of Combinatorial Theory Series B
The k-Disjoint Paths Problem on Chordal Graphs
Graph-Theoretic Concepts in Computer Science
Contractions of planar graphs in polynomial time
ESA'10 Proceedings of the 18th annual European conference on Algorithms: Part I
Edge contractions in subclasses of chordal graphs
TAMC'11 Proceedings of the 8th annual conference on Theory and applications of models of computation
Contracting a chordal graph to a split graph or a tree
MFCS'11 Proceedings of the 36th international conference on Mathematical foundations of computer science
On graph contractions and induced minors
Discrete Applied Mathematics
Containment relations in split graphs
Discrete Applied Mathematics
Edge contractions in subclasses of chordal graphs
Discrete Applied Mathematics
Increasing the minimum degree of a graph by contractions
IPEC'11 Proceedings of the 6th international conference on Parameterized and Exact Computation
Detecting induced star-like minors in polynomial time
Journal of Discrete Algorithms
Finding small separators in linear time via treewidth reduction
ACM Transactions on Algorithms (TALG)
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The k-Disjoint Paths problem, which takes as input a graph G and k pairs of specified vertices (si,ti), asks whether G contains k mutually vertex-disjoint paths Pi such that Pi connects si and ti, for i=1,…,k. We study a natural variant of this problem, where the vertices of Pi must belong to a specified vertex subset Ui for i=1,…,k. In contrast to the original problem, which is polynomial-time solvable for any fixed integer k, we show that this variant is NP-complete even for k=2. On the positive side, we prove that the problem becomes polynomial-time solvable for any fixed integer k if the input graph is chordal. We use this result to show that, for any fixed graph H, the problems H-Contractibility and H-Induced Minor can be solved in polynomial time on chordal graphs. These problems are to decide whether an input graph G contains H as a contraction or as an induced minor, respectively.