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Algorithms for finding an independent $\{K_1,K_2\}$-packing of maximum weight in a graph
V. V. Lepin Institute of Mathematics of the National Academy of Sciences of Belarus
Abstract:
Let
$\mathcal{H}$ be a fixed set of connected graphs. A
$\mathcal{H}$-packing of a given graph
$G$ is a pairwise vertex-disjoint set of subgraphs of
$G,$ each isomorphic to a member of
$\mathcal{H}$. An independent
$\mathcal{H}$-packing of a given graph
$G$ is an
$\mathcal{H}$-packing of
$G$ in which no two subgraphs of the packing are joined by an edge of
$G$. Given a graph
$G$ with a vertex weight function
$\omega_V:~V(G)\to\mathbb{N}$ and an edge weight function and
$\omega_E:~E(G)\to\mathbb{N}$. Weight of an independent
$\{K_1,K_2\}$-packing
$S$ in
$G$ is $\sum_{v\in U}\omega_V(v)+\sum_{e\in F}\omega_E(e),$ where $U=\bigcup_{G_i\in\mathcal{S},~G_i\cong K_1}V(G_i),$ and
$F=\bigcup_{G_i\in\mathcal{S}}E(G_i)$. The problem of finding an independent
$\{K_1,K_2\}$-packing of maximum weight is considered. We present algorithms to solve this problem for trees in time
$O(n)$, for unicyclic graphs in time
$O(n^2)$, and cographs and thin spider graphs in time
$O(n+m)$, for co-gem-free graphs in time
$O(m(m+n))$, where
$n$ and
$m$ are the number of vertices and edges in the graph. Moreover, we give a robust
$O(m(m+n))$ time algorithm solving this problem for the graph class $\mathcal{T}\cup\mathcal{U}\cup\mathcal{G}_1\cup\mathcal{G}_2\cup\mathcal{G}_3$, where
$\mathcal{T}$ — trees,
$\mathcal{U}$ — unicycle,
$\mathcal{G}_1$ — (bull,fork)-free,
$\mathcal{G}_2$ — (co-P,fork)-free,
$\mathcal{G}_3$ — (
$P_5,$fork)-free graphs.
UDC:
519.1 Received: 10.01.2014