adding elements of a vector to an unordered set

Question

Is there an easy way to add all the elements of a vector to an unordered_set? They are of the same type. Right now, I am using a for loop and was wondering if there is a better way to do it

Little

Answer 1

If you're constructing the unordered_set then:

std::vector<int> v;
std::unordered_set<int> s(v.begin(), v.end());

Mirtamirth

what should be done next? I've tried this, but it doesn't seem to build the set. E.g. vector<int> v; set<int> s(v.begin(), v.end()); for(...) // here I push back elements for( auto i : s) cout << i; doesn't print anything, and debugging shows the set is empty. – Subscript

Answer 2

Forgive me if my syntax has any minor bugs, but you can try the std::copy function, its meant for this purpose.

std::vector<int> v;
std::unordered_set<int> s;
std::copy(v.begin(),v.end(),std::inserter(s,s.end()));

Emaciated

std::inserter is required to insert into an associative container. – Drucilladrucy

yup, i knew i missed something, fixed. – Emaciated

does s.end() remain valid even if the container rehashes? – Selry

if v is empty then an 0 will be added to s! – Gildea