确保std::map在编译时具有具体大小的优雅方法

#include <iostream>
#include <map>

template <size_t N>
struct MapWithSize {
    static constexpr size_t size = N;
};

template <typename T, size_t N, typename... Args>
constexpr auto createMapWithSize(Args&&... args) {
    return MapWithSize<N>{{std::forward<Args>(args)...}};
}

int main() {
    constexpr auto mapWithSize = createMapWithSize<std::string, 3>(
        std::make_pair("key1", "value1"),
        std::make_pair("key2", "value2"),
        std::make_pair("key3", "value3")
    );

    std::cout << "Map size: " << mapWithSize.size << std::endl;

    std::map<std::string, std::string> myMap(mapWithSize.begin(), mapWithSize.end());
    
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}