Directed graph with million of nodes, most with only a few edges but a few with hundreds of thousands

Question

Suppose a directed graph has a million nodes, most nodes have only a few edges, but a few nodes have hundreds of thousands of edges.

To represent this graph, I used an adjacency matrix but, as it turns out, its running time is O(n²) and for adjacency matrix random access is not efficient.

How can I represent this graph in an efficient way that could solve both random access and works faster?

Answer 1

use the adjacency list, see a description here