multimap::emplace() in C++ STL

The multimap::emplace() is a built-in function in C++ STL which inserts the key and its element in the multimap container. It effectively increases the container size by one as multimap is the container that stores multiple keys with same values.

Syntax:

multimap_name.emplace(key, element)

Parameters: The function accepts two mandatory parameters which are described below:

• key – specifies the key to be inserted in the multimap container.
• element – specifies the element to the key which is to be inserted in the multimap container.

Return Value: The function does not return anything.

// C++ program for the illustration of
// multimap::emplace() function
#include <bits/stdc++.h>
using namespace std;

int main()
{

    // initialize container
    multimap<int, int> mp;

    // insert elements in random order
    mp.emplace(2, 30);
    mp.emplace(1, 40);
    mp.emplace(2, 60);
    mp.emplace(2, 20);
    mp.emplace(1, 50);
    mp.emplace(4, 50);

    // prints the elements
    cout << "\nThe multimap is : \n";
    cout << "KEY\tELEMENT\n";
    for (auto itr = mp.begin(); itr != mp.end(); itr++)
        cout << itr->first << "\t" << itr->second << endl;

    return 0;
}

Output:

The multimap is : 
KEY    ELEMENT
1    40
1    50
2    30
2    60
2    20
4    50