pub fn johnson_path_directed(
digraph: &DiGraph,
weight_attr: &str,
) -> Option<Vec<(String, Vec<(String, Vec<String>)>)>>Expand description
Johnson all-pairs shortest paths for directed graphs.
Computes Bellman-Ford potentials from an implicit super-source, reweights
the existing directed CSR edge weights once, then runs the same native
Dijkstra path kernel used by all_pairs_dijkstra_directed. Returns None
when the Bellman-Ford phase detects a negative cycle.