Editing Directed acyclic graph (section)

=== Closure problem ===
{{Main|Closure problem}}
The [[closure problem]] takes as input a vertex-weighted directed acyclic graph and seeks the minimum (or maximum) weight of a closure – a set of vertices ''C'', such that no edges leave ''C''. The problem may be formulated for directed graphs without the assumption of acyclicity, but with no greater generality, because in this case it is equivalent to the same problem on the condensation of the graph. It may be solved in polynomial time using a reduction to the [[maximum flow problem]].<ref>{{citation
 | last = Picard | first = Jean-Claude
 | doi = 10.1287/mnsc.22.11.1268
 | issue = 11
 | journal = [[Management Science (journal)|Management Science]]
 | mr = 0403596
 | pages = 1268–1272
 | title = Maximal closure of a graph and applications to combinatorial problems
 | volume = 22
 | year = 1976}}.</ref>