Both proposed possibilities (std::swap and std::iter_swap) work, they just have a slightly different syntax.
Let's swap a vector's first and second element, v[0] and v[1].
We can swap based on the objects contents:
std::swap(v[0],v[1]);
Or swap based on the underlying iterator:
std::iter_swap(v.begin(),v.begin()+1);
Try it:
int main() {
int arr[] = {1,2,3,4,5,6,7,8,9};
std::vector<int> * v = new std::vector<int>(arr, arr + sizeof(arr) / sizeof(arr[0]));
// put one of the above swap lines here
// ..
for (std::vector<int>::iterator i=v->begin(); i!=v->end(); i++)
std::cout << *i << " ";
std::cout << std::endl;
}
Both times you get the first two elements swapped:
2 1 3 4 5 6 7 8 9