std::swap(std::flat_map)

#include <algorithm>
#include <iostream>
#include <flat_map>
 
int main()
{
 std::flat_map <int, char> alice{{1, 'a'}, {2, 'b'}, {3, 'c'}};
 std::flat_map <int, char> bob{{7, 'Z'}, {8, 'Y'}, {9, 'X'}, {10, 'W'}};
 
 auto print = [](std::pair <const int, char>& n)
 {
 std::cout << ' ' << n.first << ':' << n.second;
 };
 
 // Print state before swap
 std::cout << "Alice:";
 std::for_each (alice.begin(), alice.end(), print);
 std::cout << "\nBobby:";
 std::for_each (bob.begin(), bob.end(), print);
 std::cout << '\n';
 
 std::cout << "-- SWAP\n";
 std::swap (alice, bob);
 
 // Print state after swap
 std::cout << "Alice:";
 std::for_each (alice.begin(), alice.end(), print);
 std::cout << "\nBobby:";
 std::for_each (bob.begin(), bob.end(), print);
 std::cout << '\n';
}

Alice: 1:a 2:b 3:c
Bobby: 7:Z 8:Y 9:X 10:W
-- SWAP
Alice: 7:Z 8:Y 9:X 10:W
Bobby: 1:a 2:b 3:c