std::swap(std::basic_string)
From cppreference.com
                    
                                        
                    < cpp | string | basic string
                    
                                                            
                    | template< class CharT, class Traits, class Alloc > void swap( basic_string<CharT, Traits, Alloc> &lhs, basic_string<CharT, Traits, Alloc> &rhs ); | ||
Specializes the std::swap algorithm for std::basic_string. Swaps the contents of lhs and rhs. Equivalent to lhs.swap(rhs).
Parameters
| lhs, rhs | - | strings whose contents to swap | 
Return value
(none)
Complexity
Constant.
Exceptions
| noexcept specification:  
 noexcept(noexcept(lhs.swap(rhs))) | (since C++17) | 
See also
| swaps the contents (public member function) |