C++ data structure for an undirected graph of unknown size

Question

I'm trying to make a program that explores an undirected graph of an unknown size and builds an adjacency list as it goes. Normally I would make a set<set<String>> (the rooms are identified by a string) but I've been told this is unstable in C++. What would be a better data structure?

Answer 1

It depends on how you want to query the information later.

I can suggest two alternatives:

using namespace std;
set< pair<string,string> >

or

using namespace std;
multimap<string,string>

In the first case set , you can check if two nodes are connected but you need to know both nodes (A and B) to run a query. In the second case multimap , given node A you can easily obtain an iterator with all adjacent nodes.

You will need to insert pairs twice or use some rule like always adding edges in lexicographical order.