void swap (set& x);

#include <iostream>
#include <set>

using namespace std;

int main(void) {
   set<int> m1 = {1,2,3,4,5};


   set<int> m2;

   m2.swap(m1);

   cout << "Set contains following elements" << endl;

   for (auto it = m2.begin(); it != m2.end(); ++it)
      cout << *it<< endl;

   return 0;
}

Set contains following elements
1
2
3
4
5

#include <iostream>
#include <set>

using namespace std;

 int main () {
   int myints[] = {10,20,30,40,50,60};
   set<int> first (myints,myints+3);
   set<int> second (myints+3,myints+6);  

   first.swap(second);

   cout << "first set contains:";
   for (set<int>::iterator it = first.begin(); it!=first.end(); ++it)
      cout << ' ' << *it;
   cout << '\n';

   cout << "second set contains:";
   for (set<int>::iterator it = second.begin(); it!=second.end(); ++it)
      cout << ' ' << *it;
   cout << '\n';

   return 0;
}

first set contains: 40 50 60
second set contains: 10 20 30

#include<iostream>
#include<set>
using namespace std;

int main()
{
    // Take any two sets
    set<char> set1, set2;

    set1 = {'a','b','c','d'}; 
    set2 = {'x','y','z'};

    // Swap elements of sets
    swap(set1, set2);

    // Print the elements of sets
    cout << "set1:\n";
    for (auto it = set1.begin(); it != set1.end(); it++)
        cout << "\t" << *it<< '\n';

    cout << "set2:\n";
    for (auto it = set2.begin(); it != set2.end(); it++)
        cout << "\t" << *it<< '\n';

    return 0;
}

set1:
    x
    y
    z
set2:
    a
    b
    c
    d

#include <set>  
#include <iostream>  

int main( )  
{  
   using namespace std;  
   set <int> s1, s2, s3;  
   set <int>::iterator s1_Iter;  

   s1.insert( 10 );  
   s1.insert( 20 );  
   s1.insert( 30 );  
   s2.insert( 100 );  
   s2.insert( 200 );  
   s3.insert( 300 );  

   cout << "The original set s1 is:";  
   for ( s1_Iter = s1.begin( ); s1_Iter != s1.end( ); s1_Iter++ )  
      cout << " " << *s1_Iter;  
   cout   << "." << endl;  

   // This is the member function version of swap  
   s1.swap( s2 );  

   cout << "After swapping with s2, list s1 is:";  
   for ( s1_Iter = s1.begin( ); s1_Iter != s1.end( ); s1_Iter++ )  
      cout << " " << *s1_Iter;  
   cout  << "." << endl;  

   // This is the specialized template version of swap  
   swap( s1, s3 );  

   cout << "After swapping with s3, list s1 is:";  
   for ( s1_Iter = s1.begin( ); s1_Iter != s1.end( ); s1_Iter++ )  
      cout << " " << *s1_Iter;  
   cout   << "." << endl;  
}  

The original set s1 is: 10 20 30.
After swapping with s2, list s1 is: 100 200.
After swapping with s3, list s1 is: 300.