How to Create a Multimap of Arrays in C++?

In C++, a multimap is similar to a map with the addition that multiple elements can have the same keys. Also, it is NOT required that the key-value and mapped value pair have to be unique in this case. In this article, we will learn how to create a multimap of arrays in C++ STL.

Example

Input:
myArray1 = [“John”, “Doe”];
myArray2 = [“Adam”, “Smith”];

Output:
Multimap: {1 -> [“John”, “Doe”], 2 -> [“Adam”, “Smith”]}

Multimap of Arrays in C++ STL

In C++ STL, you can create a multimap of arrays by specifying the array type as the value type of the multimap. We can choose the key of our desired type. After that, we can insert the element into the multimap using the std::multimap::insert() function.

Syntax

multimap<int, array<int, 5> > myMultimap;

C++ Program to Create a Multimap of Arrays

C++

// C++ Program to illustrate how to Create a Multimap of
// Arrays
#include <array>
#include <iostream>
#include <map>
using namespace std;

int main()
{
    // Declaration of the multimap with array type as values
    multimap<int, array<int, 5> > map;

    // Declaration of the arrays
    array<int, 5> arr1 = { 10, 20, 30, 40, 50 };
    array<int, 5> arr2 = { 1, 3, 5, 7, 9 };

    // Inserting keys and their respective arrays into the
    // multimap
    map.insert({ 1, arr1 });
    map.insert({ 2, arr2 });

    // Printing the keys and their respective arrays
    for (const auto& pair : map) {
        cout << "Key: " << pair.first << ", Values: ";
        for (int item : pair.second) {
            cout << item << " ";
        }
        cout << endl;
    }

    return 0;
}

Output

Key: 1, Values: 10 20 30 40 50 
Key: 2, Values: 1 3 5 7 9 

Time Complexity: O(N * logN), where N is the number of arrays.
Space Complexity: O(N * M), where M is the average size of the arrays.