Summary

A directed_graph has ordered edges connecting one vertex to another. It is commonly stored as an adjacency_list or an adjacency_matrix. Each node has an in_degree and an out_degree. A path follows edge direction. A cycle returns to its start; a directed_acyclic_graph has none. Some graphs use weighted_edges; others are unweighted. A single node linking to itself is a self_loop. Basic tasks include reachability and traversal.