怎么使用std::foreach遍历unorderedmap

可以使用C++11的范围for循环或者std::for_each来遍历unordered_map。下面是两种方法的示例：

1. C++11的范围for循环

#include <iostream>
#include <unordered_map>

int main()
{
    std::unordered_map<std::string, int> mymap = {{"apple", 1}, {"banana", 2}, {"cherry", 3}};

    for (auto& pair : mymap) {
        std::cout << pair.first << ": " << pair.second << '\n';
    }

    return 0;
}

输出:

apple: 1
banana: 2
cherry: 3

2. std::for_each

#include <iostream>
#include <unordered_map>
#include <algorithm>

int main()
{
    std::unordered_map<std::string, int> mymap = {{"apple", 1}, {"banana", 2}, {"cherry", 3}};

    std::for_each(mymap.begin(), mymap.end(), [](const auto& pair) {
        std::cout << pair.first << ": " << pair.second << '\n';
    });

    return 0;
}

输出:

apple: 1
banana: 2
cherry: 3