How To Insert Multiple Key-Value Pairs Into a Multimap in C++?

In C++, a multimap is similar to a map that stores the data in the key-value format and it also allows us to store duplicate keys for the same value. In this article, we will learn how to insert multiple Key-Value pairs efficiently into a multimap.

Example:

Input: 
multi_map = {{"Manas","Singing" }, {"Manas","Dancing" }}

Output:
Multimap after Insertion:
Manas-> Singing
Manas-> Dancing
Salma-> Reading
Salma-> Painting
Salma-> Arts
Soumya-> Music

Add Multiple Key-Value Pairs in a Multimap in C++

We can use the std::multimap::insert in C++ STL to insert elements in the std::multimap container by passing all the key-value pairs inside the insert() function at once.

C++ Program to Add Multiple Key-Value Pairs in a Multimap

The below program demonstrates how we can insert multiple key-value pairs at a time in a multimap in C++ STL.

// C++ Program insert Multiple Items Into a Multimap

#include <iostream>
#include <map>
using namespace std;

int main()
{
    multimap<string, string> hobbies
        = { { "Manas", "Singing" },
            { "Manas", "Dancing" } };

    // inserting multiple key-value pairs in a map

    hobbies.insert({ { "Salma", "Reading" },
                     { "Soumya", "Music" },
                     { "Salma", "Painting" },
                     { "Salma", "Arts" } });

    // Displaying the elements pf multimap
    cout << "Multimap after Insertion: " << endl;
    for (const auto& key_value : hobbies) {
        string key = key_value.first;
        string value = key_value.second;
        cout << key << "-> " << value << endl;
    }
    return 0;
}

Multimap after Insertion: 
Manas-> Singing
Manas-> Dancing
Salma-> Reading
Salma-> Painting
Salma-> Arts
Soumya-> Music

Time Complexity: O(M * log(N)), where N is the number of elements in the multimap and M is the number of elements to be inserted.
Auxilliary Space: O(M)