The back_insert_iterator is an iterator adapter that acts as an output iterator, but which converts expressions of the form *itr = value into calls to push_back on an STL container. The back_insert_iterator constructor takes in a reference to another STL container class that should have push_back invoked on it. Because the back_insert_iterator calls push_back on the element it wraps, the container type must support the push_back function. Consequently, you cannot use a back_insert_iterator on an STL map or set; for those classes, consider using insert_iterator.
back_insert_iterator is a template type whose argument is the type of container to which the back_insert_iterator should forward its requests. For example, to invoke push_back on a container of type vector<int>, you would use a back_insert_iterator<vector<int> >. Remember to include the extra space between the closing angle brackets or you will get a compile-time error!
Since the above syntax can get a bit clunky, the STL provides a utility function, back_inserter, which creates back_insert_iterators.
back_insert_iterator<Container> Utility FunctionsConstructs a new back_insert_iterator that calls push_back on the element specified as the parameter when dereferenced. It is preferable to create back_insert_iterators using back_inserter rather than through a constructor call, since the compiler will figure out the correct type of back_insert_iterator to create. Since in most cases you will create back_insert_iterators as parameters to functions, this function also lets you avoid writing out the type of the back_insert_iterator longhand.
back_insert_iterator<Container> Member Functionsback_insert_iterator on the specified element.Constructs a new back_insert_iterator that calls push_back on the element specified as the parameter when dereferenced.