STL-map

最新推荐文章于 2025-02-20 16:28:40 发布

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本文通过一个具体的示例介绍了C++标准库中map容器的使用方法，包括map的基本操作如插入元素、交换两个map的内容等，并展示了迭代器和引用在容器操作中的行为特性。

C++中map的详细用法

引用

#include <iostream>
#include <string>
#include <utility>
#include <map>
 
// print out a std::pair
template <class Os, class U, class V>
Os& operator<<(Os& os, const std::pair<U, V>& p) {
    return os << p.first << ":" << p.second;
}
 
// print out a container
template <class Os, class Co>
Os& operator<<(Os& os, const Co& co) {
    os << "{";
    for (auto const& i : co) { os << ' ' << i; }
    return os << " }\n";
}
 
int main()
{
    std::map<std::string, std::string>
        m1 { {"γ", "gamma"}, {"β", "beta"}, {"α", "alpha"}, {"γ", "gamma"}, },
        m2 { {"ε", "epsilon"}, {"δ", "delta"}, {"ε", "epsilon"} };
 
    const auto& ref = *(m1.begin());
    const auto iter = std::next(m1.cbegin());
 
    std::cout << "──────── before swap ────────\n"
              << "m1: " << m1 << "m2: " << m2 << "ref: " << ref
              << "\niter: " << *iter << '\n';
 
    m1.swap(m2);
 
    std::cout << "──────── after swap ────────\n"
              << "m1: " << m1 << "m2: " << m2 << "ref: " << ref
              << "\niter: " << *iter << '\n';
 
    // Note that every iterator referring to an element in one container before
    // the swap refers to the same element in the other container after the swap.
    // Same is true for references.
}