C++ unordered_map遍歷有哪些方法

在C++中，可以使用以下方法來遍歷unordered_map：

1. 使用迭代器遍歷：

std::unordered_map<int, std::string> myMap = {{1, "apple"}, {2, "banana"}, {3, "orange"}};
for(auto it = myMap.begin(); it != myMap.end(); ++it) {
    std::cout << "Key: " << it->first << ", Value: " << it->second << std::endl;
}

2. 使用范圍-based for 循環遍歷：

std::unordered_map<int, std::string> myMap = {{1, "apple"}, {2, "banana"}, {3, "orange"}};
for(const auto& pair : myMap) {
    std::cout << "Key: " << pair.first << ", Value: " << pair.second << std::endl;
}

3. 使用for_each遍歷：

std::unordered_map<int, std::string> myMap = {{1, "apple"}, {2, "banana"}, {3, "orange"}};
std::for_each(myMap.begin(), myMap.end(), [](const std::pair<int, std::string>& pair) {
    std::cout << "Key: " << pair.first << ", Value: " << pair.second << std::endl;
});

4. 使用范圍-based for 循環遍歷鍵或值：

std::unordered_map<int, std::string> myMap = {{1, "apple"}, {2, "banana"}, {3, "orange"}};
for(const auto& pair : myMap) {
    std::cout << "Key: " << pair.first << std::endl;
}

for(const auto& pair : myMap) {
    std::cout << "Value: " << pair.second << std::endl;
}