C++ 程序：STL 多重映射

原文：https://www.studytonight.com/cpp-programs/cpp-stl-multimap-program

大家好！

在本教程中，我们将学习 C++ 编程语言中 STL 中多重映射的概念。

要了解 STL 中映射容器的基本功能，我们将推荐您访问https://www.studytonight.com/cpp/stl/stl-container-map，我们已经从头开始详细解释了这个概念。

什么是多重映射？

多重映射类似于映射，具有两个附加功能:

1. 多个元素可以有相同或重复的键。

2. 多个元素可以有相同或重复的键值对。

为了更好地理解它的实现，请参考下面给出的注释良好的 C++ 代码。

代号:

#include <iostream>
#include <bits/stdc++.h>

using namespace std;

int main()
{
    cout << "\n\nWelcome to Studytonight :-)\n\n\n";
    cout << " =====  Program to demonstrate the concept of Multimap (Part 1), in CPP  ===== \n\n\n";

    cout << " Multimap is similar to map with two additional functionalities: \n1\. Multiple elements can have same keys or \n2\. Multiple elements can have same key-value pair.\n\n";

    //Multimap declaration (Multimap with key and value both as integers)
    multimap<int, int> m;

    //Filling the elements by using the insert() method.
    cout << "Filling the Multimap with key-value pairs of integers in random order."; //Map automatically stores them in increasing order of keys

    //make_pair() is used to insert a key value pair into the map
    m.insert(make_pair(3, 30));
    m.insert(make_pair(2, 20));
    m.insert(make_pair(5, 50));
    m.insert(make_pair(9, 90));
    m.insert(make_pair(1, 10));
    m.insert(make_pair(3, 30));
    m.insert(make_pair(3, 60));

    cout << "\n\nThe number of elements in the Multimap are: " << m.size();

    cout << "\n\nThe elements of the Multimap m are: ";

    multimap<int, int>::iterator i;

    for (i = m.begin(); i != m.end(); i++)
    {
        cout << "( " << i->first << ", " << i->second << " ) ";
    }

    //Copying one multimap into another
    multimap<int, int> m1(m.begin(), m.end());

    cout << "\n\nThe elements of the Multimap m1 are: ";

    for (i = m1.begin(); i != m1.end(); i++)
    {
        cout << "( " << i->first << ", " << i->second << " ) ";
    }

    cout << "\n\n\n";

    return 0;
}

输出:

我们希望这篇文章能帮助你更好地理解 STL 中多重映射容器的概念及其在 C++ 中的实现。如有任何疑问，请随时通过下面的评论区联系我们。

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