In C++, a multimap is a container that stores key-value pairs in an ordered manner. Unlike a map, a multimap allows multiple values to be associated with a single key. In this article, we will learn how to insert into a multimap using make_pair in C++.

Example

Input: 
myMultimap = {{1, “C++”}, {2, “Java”}};
Pair to Insert: {1, “Python”};

Output:
myMultimap = {1, C++}, {1, Python}, {2, Java}

Insert into Multimap using make_pair in C++

The std::make_pair() function constructs a pair of the given type and returns this pair. We can use this function to create a pair and directly insert it into the multimap container using std::multimap::insert(). Note that the pair type and multimap type should be the same.

Syntax

multiMap.insert(make_pair(1, "apple"));

Where 1 is the key and "apple" is the associated value.

C++ Program to Insert into Multimap using make_pair

// C++ Program to illustrate how to insert into a multimap
// using make_pair
#include <iostream>
#include <map>
using namespace std;

int main()
{
    // Initialize a multimap with some entries
    multimap<int, string> myMultimap
        = { { 1, "C++" }, { 2, "Java" } };

    // Insert a new pair into the multimap using make_pair
    myMultimap.insert(make_pair(1, "Python"));

    // Print the multimap after insertion
    for (auto& pair : myMultimap) {
        cout << "{" << pair.first << ", " << pair.second
             << "}, ";
    }
    cout << endl;

    return 0;
}

// C++ Program to illustrate how to insert into a multimap

// using make_pair

#include <iostream>

#include <map>

using namespace std;

​

int main()

{

    // Initialize a multimap with some entries

    multimap<int, string> myMultimap

        = { { 1, "C++" }, { 2, "Java" } };

​

    // Insert a new pair into the multimap using make_pair

    myMultimap.insert(make_pair(1, "Python"));

​

    // Print the multimap after insertion

    for (auto& pair : myMultimap) {

        cout << "{" << pair.first << ", " << pair.second

             << "}, ";

    }

    cout << endl;

​

    return 0;

}

{1, C++}, {1, Python}, {2, Java}, 

Time Complexity: O(logN) where N is the number of elements in the multimap.
Auxiliary Space: O(1)