c ++通过引用将映射传递给函数

#include<iostream>
#include <map>

void print_map(const std::map<int, std::string>& m) {
    for (const auto& p : m) {
        std::cout << p.first << ": " << p.second<< std::endl;
    }
}

void modify_map(std::map<int, std::string>& m) {
    m[4] = "four";
    m[5] = "five";
}

int main() {
    std::map<int, std::string> my_map = {{1, "one"}, {2, "two"}, {3, "three"}};

    std::cout << "Original map:"<< std::endl;
    print_map(my_map);

    modify_map(my_map);

    std::cout << "Modified map:"<< std::endl;
    print_map(my_map);

    return 0;
}