Question

I read some code written in c++ as following:

#include <algorithm>
#include <iostream> 
#include <vector>

using namespace std;

int main() {
    int iarr[] = {30, 12, 55, 31, 98, 11, 41, 80, 66, 21};
    vector<int> ivector(iarr, iarr + 10);
}

in the above code, I pass iarr and iarr+10 to ivector(iarr, iarr + 10) to create a new vector, is this a proper way to construct a vector? I checked the STL document, it is not mentioned there, is this allowed?

and also, array iarr contains 10 elements, should I use ivector(iarr, iarr+9)?

Answer 1

Yes, it is allowed and yes, you are doing it right.

You are calling this templated constructor:

template<class InputIterator>
   vector(
      InputIterator _First,
      InputIterator _Last
   );

The template parameter InputIterator is int* (this is the type of the expressions iarr and iarr + 10).

Since the documentation states that _Last must point to one element beyond the last in the range, the + 10 is also correct to copy all 10 elements in the array (iarr + 9 points to the last element, iarr + 10 points to one beyond the last element).