A **`multimap`** can store more than one value against a key. Both keys and values are stored in the form of a tuple. A `multimap` is similar to a `map` in C+; the only difference is that a `multimap` can hold keys that are not unique (unlike in a standard map).
See the example below of how to insert a pair into `myMap <int,char>` and `myMultimap <int, char>`. 

The following code is used to insert the pair in the `map`:

```C++

myMap.insert(pair <int, char>
(1, 'a'));
//This will assign 1 as a key and 
//'a' as a value

//WE CANNOT DO THE 
//FOLLOWING IN MAPS

myMap.insert(pair <int, char> 
(1, 'e')); //Will give error

//Since it is important for 
//a single key to have 
//a single value

``` 
However, in a `multimap`, a user can assign two values to a single key:​

```C++
myMultimap.insert(pair <int, char>
(1, 'a'));
//This will assign 1 as a key and 
//'a' as a value

myMap.insert(pair <int, char> 
(1, 'e')); //Assigned 'e' to
//key 1

//Now Key 1 looks like
// 1 --> a
// 1 --> b 

```



# Idea illustration

The following illustration explains this concept better:

# Code
The code snippet below implements the illustration above​:

#include <iostream> 
#include <map> 
#include <iterator> 
  
using namespace std; 
  
int main() 
{ 
    multimap <int, char> gquiz1;        // empty multimap container 
  
    // insert elements in random order 
    gquiz1.insert(pair <int, int> (1, 'a')); 
    /*gquiz1.insert(pair <int, int> (2, 30)); 
    gquiz1.insert(pair <int, int> (3, 60)); 
    gquiz1.insert(pair <int, int> (4, 20)); 
    gquiz1.insert(pair <int, int> (5, 50)); 
    gquiz1.insert(pair <int, int> (6, 50)); 
    gquiz1.insert(pair <int, int> (6, 10)); 
    */
  
    // printing multimap gquiz1 
    multimap <int, char> :: iterator itr; 
    cout << "\nThe multimap gquiz1 is : \n"; 
    cout << "\tKEY\tELEMENT\n"; 
    for (itr = gquiz1.begin(); itr != gquiz1.end(); ++itr) 
    { 
        cout  <<  '\t' << itr->first 
              <<  '\t' << itr->second << '\n'; 
    } 
    cout << endl; 
  
} 


What is a multimap in C++?

Idea illustration

Code