std::unordered_map::swap
From cppreference.com
                    
                                        
                    < cpp | container | unordered map
                    
                                                            
                    
| void swap( unordered_map& other ); | (since C++11) (until C++17) | |
| void swap( unordered_map& other ) noexcept(/* see below */); | (since C++17) | |
Exchanges the contents of the container with those of other. Does not invoke any move, copy, or swap operations on individual elements.
All iterators and references remain valid. The past-the-end iterator is invalidated.
The Hash and KeyEqual objects must be Swappable, and they are exchanged using unqualified calls to non-member swap.
| If std::allocator_traits<allocator_type>::propagate_on_container_swap::value is true, then the allocators are exchanged using an unqualified call to non-member swap. Otherwise, they are not swapped (and if get_allocator() != other.get_allocator(), the behavior is undefined). | (since C++11) | 
| Contents | 
[edit] Parameters
| other | - | container to exchange the contents with | 
[edit] Return value
(none)
[edit] Exceptions
| Any exception thrown by the swap of the  | (until C++17) | 
| noexcept specification:  
 noexcept(std::allocator_traits<Allocator>::is_always_equal::value && std::is_nothrow_swappable<Hash>::value | (since C++17) | 
[edit] Complexity
Constant.
[edit] See also
| specializes the std::swap algorithm (function template) | 


