map emplace与try_emplace的行为？

template< class... Args >
pair<iterator,bool> emplace( Args&&... args );

template< class... Args >
pair<iterator,bool> try_em::place( const Key& key, Args&&... args );
template< class... Args >
pair<iterator,bool> try_emplace( Key&& key, Args&&... args );

#include <iostream>
#include <map>

int main() {
    std::map<int, std::string> myMap;

    // 使用 emplace 插入元素
    auto result1 = myMap.emplace(1, "Hello");
    if (result1.second) {
        std::cout << "Element emplaced successfully." << std::endl;
    } else {
        std::cout << "Element already exists." << std::endl;
    }

    // 使用 try_emplace 插入元素
    auto result2 = myMap.try_emplace(2, "World");
    if (result2.second) {
        std::cout << "Element emplaced successfully." << std::endl;
    } else {
        std::cout << "Element already exists." << std::endl;
    }

    // 尝试使用 try_emplace 插入已存在的键
    auto result3 = myMap.try_emplace(1, "New Value");
    if (result3.second) {
        std::cout << "Element emplaced successfully." << std::endl;
    } else {
        std::cout << "Element already exists, no change made." << std::endl;
    }

    return 0;
}