Covering Directed Graphs by In-trees

Naoyuki Kamiyama, Naoki Katoh

Given a directed graph $D=(V,A)$ with a set of $d$ specified vertices $S=\{s_1,...,s_d\}\subseteq V$ and a function $f:S\to {\mathbb{Z}}_{+}$ where ${\mathbb{Z}}_{+}$ denotes the se…