|igraph Reference Manual|
int igraph_maximal_cliques(const igraph_t *graph, igraph_vector_ptr_t *res);
A maximal clique is a clique which can't be extended any more by adding a new vertex to it. This is actually implemented by looking for a maximal independent vertex set in the complementer of the graph.
If you are only interested in the size of the largest clique in the graph,
The input graph.
Pointer to a pointer vector, the result will be stored
Time complexity: TODO.