`Degrees degrees(const G& g)`

returns array of node degrees
return as the following structure:

struct Degrees { array<unsigned> in_degree, out_degree; };

+void ErdosRenyi_generate(Graph& g, unsigned nodes, unsigned links, urand& uni);+

Generate an Erdös-Rényi random graph with given nodes and links. Links are attached randomly to the nodes, drawn from uni.

+PreferentialAttach_generate(Graph& g, unsigned nodes, urand& uni, random_gen& indegree_dist=default_indegree)+

Barabasi-Albert Preferential attachment algorithm. For each node, an
indegree value is drawn from `indegree_dist`

(defaults to a
constant value of 1). This many links are then preferentially attached
to other nodes, according to their outdegree.