Finding $k$ Disjoint Paths in a Directed Planar Graph
SIAM Journal on Computing
Graph minors. XIII: the disjoint paths problem
Journal of Combinatorial Theory Series B
NP-completeness of some edge-disjoint paths problems
Discrete Applied Mathematics
Decision algorithms for unsplittable flow and the half-disjoint paths problem
STOC '98 Proceedings of the thirtieth annual ACM symposium on Theory of computing
A Polynomial Solution to the Undirected Two Paths Problem
Journal of the ACM (JACM)
Paths, Flows, and VLSI-Layout
Approximation Algorithms for Single-Source Unsplittable Flow
SIAM Journal on Computing
On the k-Splittable Flow Problem
ESA '02 Proceedings of the 10th Annual European Symposium on Algorithms
Single-source unsplittable flow
FOCS '96 Proceedings of the 37th Annual Symposium on Foundations of Computer Science
Approximation algorithms for disjoint paths problems
Approximation algorithms for disjoint paths problems
Parameterized Complexity Theory (Texts in Theoretical Computer Science. An EATCS Series)
Parameterized Complexity Theory (Texts in Theoretical Computer Science. An EATCS Series)
Hi-index | 0.00 |
Given a graph and terminal pairs $(s_i,t_i)$, $i\in[k]$, the edge-disjoint paths problem is to determine whether there exist $s_{i}t_{i}$ paths, $i\in[k]$, that do not share any edges. We consider this problem on acyclic digraphs. It is known to be NP-complete and solvable in time $n^{O(k)}$ where $n$ is the number of nodes. It has been a long-standing open question whether it is fixed-parameter tractable in $k$, i.e., whether it admits an algorithm with running time of the form $f(k)\,n^{O(1)}$. We resolve this question in the negative: we show that the problem is $W[1]$-hard, hence unlikely to be fixed-parameter tractable. In fact it remains $W[1]$-hard even if the demand graph consists of two sets of parallel edges. On a positive side, we give an $O(m+k^{O(1)}\,k!\,n)$ algorithm for the special case when $G$ is acyclic and $G+H$ is Eulerian, where $H$ is the demand graph. We generalize this result (1) to the case when $G+H$ is “nearly” Eulerian, and (2) to an analogous special case of the unsplittable flow problem, a generalized version of disjoint paths that has capacities and demands.