map遍历的几种代码实现

在C++中，遍历map有以下几种方式：

方式一：使用迭代器

#include <iostream>
#include <map>

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

    for (it = myMap.begin(); it != myMap.end(); ++it)
    {
        std::cout << it->first << " " << it->second << std::endl;
    }

    return 0;
}

方式二：使用auto关键字

#include <iostream>
#include <map>

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

    for (auto it = myMap.begin(); it != myMap.end(); ++it)
    {
        std::cout << it->first << " " << it->second << std::endl;
    }

    return 0;
}

方式三：使用C++11的range-based for循环

#include <iostream>
#include <map>

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

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

    return 0;
}

方式四：使用STL算法

#include <iostream>
#include <algorithm>
#include <map>

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

    std::for_each(myMap.begin(), myMap.end(), [](std::pair<const int, std::string> &p) {
        std::cout << p.first << " " << p.second << std::endl;
    });

    return 0;
}