Obtaining list of keys and values from unordered_map

Okay, here you go:

std::vector<Key> keys;
keys.reserve(map.size());
std::vector<Val> vals;
vals.reserve(map.size());

for(auto kv : map) {
    keys.push_back(kv.first);
    vals.push_back(kv.second);  
} 

Efficiency can probably be improved, but there it is. You’re operating on two containers though, so there’s not really any STL magic that can hide that fact.

As Louis said, this will work for any of the STL map or set containers.