It is possible to specify the requested storage size of a vector during construction like this:

 #include using namespace std;int main() {  vector  vi(1000); //initial storage for 1000 int's  //vi contains 1000 elements initialized by int::int()}

Remember that vector::reserve() allocates raw memory without initializing it. The constructor, on the other hand, initializes the allocated elements by invoking their default constructor. It is possible to specify a different initializer value:

 vector  vi(1000, 4); //initialize  all 1000 int's with 4