an:06855757
Zbl 06855757
Kowaluk, Miros??aw; Lingas, Andrzej
Are unique subgraphs not easier to find?
EN
Inf. Process. Lett. 134, 57-61 (2018).
00380023
2018
j
68Q
algorithms; subgraph isomorphism; induced subgraph isomorphism; unique subgraph occurrence; time complexity
Summary: Consider a pattern graph \(H\) with \(l\) edges, and a host graph \(G\) which may contain several occurrences of \(H\). In [15], we claimed that the time complexity of the problems of finding an occurrence of \(H\) (if any) in \(G\) as well as that of the decision version of the problem are within a multiplicative factor \(\widetilde{O}(l^3)\) of the time complexity for the corresponding problem, where the host graph is guaranteed to contain at most one occurrence of a subgraph isomorphic to \(H\), and the notation \(\widetilde{O}()\) suppresses polylogarithmic in \(n\) factors. We show a counterexample to this too strong claim and correct it by providing an \(\widetilde{O}((l(d-1)+2)^l)\) bound on the multiplicative factor instead, where \(d\) is the maximum number of occurrences of \(H\) that can share the same edge in the input host graph. We provide also an analogous correction in the induced case when occurrences of induced subgraphs isomorphic to \(H\) are sought.