e weights or the number of edges between two nodes, or an exotic combination of or variation on any of those things.</li>
</ul>
</ul>
<ul>
<ul>
<li>The runtime for inserting an edge or looking up whether two vertices are adjacent in an adjacency matrix is O(1): we just jump to the corresponding cell in our array.</li>
</ul>
</ul>
<ul>
<ul>
<li>An adjacency matrix always uses O(n<sup>2</sup>) space. If we have a <strong>sparse</strong> graph, this is wasteful, and we might be better off with an adjacency lis