representing a directed graph versus undirected graph

Hi

As a learning exercise, I am writing a library for graphs. As I understand it, graphs can be represented as an adjacency list (i.e. for each node, a list of its adjacent nodes). I would like for my library to represent directed and undirected graphs - am I correct in thinking that for an undirected graph that you would keep a mirror image of adjacency lists?

So, for example, if you have an undirected graph where A and B are adjacent then A's adjacency list would include B and B's adjacency list would include A?

Thanks
 So, for example, if you have an undirected graph where A and B are adjacent then A's adjacency list would include B and B's adjacency list would include A?

Yes.
Note that a directed graph and an undirected graph are easily representable by the very same structure.

A common representation is as a 2D array, but you can use other structures in the same way. My preferred method is often something like:

 `` `` ``using graph = std::unordered_map > ;``

where `name` is the ID of the node.

If the ID is a simple integer in 0..N, then a bitset is a good choice too.
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