map::swap()_30-Seconds-of-C++, C++ (gcc)

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#include <iostream>
#include <map>

int main() { 
    // declaration of map containers of same type
    std::map<char, int> mp1, mp2;
    
    mp1['a'] = 1; 
    mp1['b'] = 2; 
    mp1['c'] = 3; 
    
    mp2['A'] = 5;
    mp2['B'] = 10;
    mp2['C'] = 11;
    
    std::map<char, int>::iterator itr;
    
    std::cout << "Key-Value pair of mp1 before swap: " << std::endl;
    for(itr = mp1.begin(); itr != mp1.end(); ++itr)
        std::cout << itr->first << " " << itr->second << std::endl;
    
    std::cout << "Key-Value pair of mp2 before swap: " << std::endl;
    for(itr = mp2.begin(); itr != mp2.end(); ++itr)
        std::cout << itr->first << " " << itr->second << std::endl;
    
    mp1.swap(mp2);
    
    std::cout << "Key-Value pair of mp1 after swap: " << std::endl;
    for(itr = mp1.begin(); itr != mp1.end(); ++itr)
        std::cout << itr->first << " " << itr->second << std::endl;
    
    std::cout << "Key-Value pair of mp2 after swap: " << std::endl;
    for(itr = mp2.begin(); itr != mp2.end(); ++itr)
        std::cout << itr->first << " " << itr->second << std::endl;
    
    return 0; 
}

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