Strongly connected components.
Functor providing functions to compute strongly connected components of a graph.
scc g computes the strongly connected components of
The result is a pair
n is the number of
components. Components are numbered from
f is a function mapping each vertex to its component
number. In particular,
f u = f v if and only if
v are in the same component. Another property of the
numbering is that components are numbered in a topological
order: if there is an arc from
f u >= f u
Not tail-recursive. Complexity: O(V+E) The function returned has complexity O(1)