what exactly does v.assign ?

Question

int main()
{
vector<int> v;
v.assign(5,3);

cout<<v.size()<<endl;
}

Answer 1

its assign a value 3 in the first 5 elements. think the vector like an array. at declaration its still empty []

on .assign(5,3) it'll assign a new size, then it'll everything with 3
[3,3,3,3,3]

more on that here https://en.cppreference.com/w/cpp/container/vector/assign