Parameterized Complexity of Path Set Packing

Abstract

In PATH SET PACKING, the input is an undirected graph $G$, a collection $\cal P$ of simple paths in $G$, and a positive integer $k$. The problem is to decide whether there exist $k$ edge-disjoint paths in $\cal P$. We study the parameterized complexity of PATH SET PACKING with respect to both natural and structural parameters. We show that the problem is $W[1]$-hard with respect to vertex cover plus the maximum length of a path in $\cal P$, and $W[1]$-hard respect to pathwidth plus maximum degree plus solution size. These results answer an open question raised in COCOON 2018. On the positive side, we show an FPT algorithm parameterized by feedback vertex set plus maximum degree, and also show an FPT algorithm parameterized by treewidth plus maximum degree plus maximum length of a path in $\cal P$. Both the positive results complement the hardness of PATH SET PACKING with respect to any subset of the parameters used in the FPT algorithms