How can I use a C++ unordered_set for a custom class?

Question

How can I store objects of a class in an unordered_set? My program needs to frequently check if an object exists in this unordered_set and if it does,

Answer 1

You could try using the following hash function object (it's pretty basic so you may want to improve it to avoid too many collisions).

struct node_hash {
    std::size_t operator()(const node& _node) const {
        return std::hash()(_node.node_id);
    }
}
// ...
std::unordered_set node_set;

However, as one of the comments points out, you may be better off using a std::unordered_map here.