unordered_set swap() function in C++ STL

The unordered_set::swap() method is a builtin function in C++ STL which is used to exchange values of two unordered_set containers. It swaps the element of two unordered_set containers. The sizes may differ but it swaps elements and changes the order of elements also.
Syntax: 

unordered_set_firstname.swap(unordered_set_secondname)

Parameter: The function accepts one mandatory parameter second_name which specifies the second unordered_set which is to be swapped with the first one. 
Return Value: This function doesn't returns anything.
Below program illustrates the unordered_set::swap() function: 

The elements of arr1 before swap(): 5 1 2 3 4 
The elements of arr2 before swap(): 9 5 6 7 8 

The elements of arr1 after swap(): 9 5 6 7 8 
The elements of arr2 after swap(): 5 1 2 3 4

Time complexity: O(1)
Auxiliary Space: O(1)