2.6. igraph_diameter — Calculates the diameter of a graph (longest geodesic).

2.6. `igraph_diameter` — Calculates the diameter of a graph (longest geodesic).

int igraph_diameter(const igraph_t *graph, igraph_integer_t *pres, 
		    igraph_integer_t *pfrom, igraph_integer_t *pto, 
		    igraph_vector_t *path,
		    igraph_bool_t directed, igraph_bool_t unconn);

Arguments:

`graph`:	The graph object.
`pres`:	Pointer to an integer, if not `NULL` then it will contain the diameter (the actual distance).
`pfrom`:	Pointer to an integer, if not `NULL` it will be set to the source vertex of the diameter path.
`pto`:	Pointer to an integer, if not `NULL` it will be set to the target vertex of the diameter path.
`path`:	Pointer to an initialized vector. If not `NULL` the actual longest geodesic path will be stored here. The vector will be resized as needed.
`directed`:	Boolean, whether to consider directed paths. Ignored for undirected graphs.
`unconn`:	What to do if the graph is not connected. If `TRUE` the longest geodesic within a component will be returned, otherwise the number of vertices is returned. (The rationale behind the latter is that this is always longer than the longest possible diameter in a graph.)

Returns:

Error code: IGRAPH_ENOMEM, not enough memory for temporary data.

Time complexity: O(|V||E|), the number of vertices times the number of edges.