In C++, deques are containers that allow efficient insertion and deletion operations from both ends. Multisets are associative containers similar to sets but unlike sets, multisets allow duplicate insertions as well. In this article, we will learn how to create a deque of multiset in C++.

Example

Input: 
mySet1 = { 1, 2, 4, 6, 7 } 
mySet2 = { 1, 3, 4 , 4 } 

Output: 
Stack of Unordered_Multiset: [ { 1, 2, 4, 6, 7 },
                            { 1, 3, 4, 4 } ]

Create a Deque of Multisets in C++

To create a std::deque of std::multisets in C++, we have to pass the type of the std::deque as std::multiset as the template parameter during the deque declaration. This will create a deque object where each element is a multiset.

Syntax to Create Deque of Multiset in C++

deque<multiset<dataType>> dq_Name;

C++ Program to Create a Deque of Multisets

The following program illustrates how to create a deque of multisets in C++:

// C++ program to illustrate how to create a deque of
// multiset
#include <deque>
#include <iostream>
#include <set>
using namespace std;

int main()
{
    // Initialize a deque of multisets
    deque<multiset<int> > dq;

    // Create  multiset with few elemnts
    multiset<int> ms1 = { 10, 20, 20, 30 };
    multiset<int> ms2 = { 1, 2, 3, 4 };

    // Insert the multisets into the deque
    dq.push_back(ms1);
    dq.push_back(ms2);

    // Print the elements of the deque
    cout << "Deque Elements: " << endl;
    int i = 1;
    for (auto it = dq.begin(); it != dq.end(); ++it) {
        cout << "MultiSet" << i << ": { ";
        for (auto x : *it) {
            cout << x << " ";
        }
        i++;
        cout << "}" << endl;
    }

    return 0;
}

Deque Elements: 
MultiSet1: { 10 20 20 30 }
MultiSet2: { 1 2 3 4 }

Time Complexity: O(N*M) where n is the number of multisets.
Auxiliary Space: O(N*M), where M is the average number of elements in the multiset.