How to Create a Stack of Multisets in C++?

In C++, a stack is a container adapter that operates in a LIFO (Last In First Out) element order and allows insertion and deletion from the end only. A multiset is a container that stores elements in an ordered manner and allows multiple instances of an element. In this article, we will learn how to create a stack of multisets in C++.

Example:

Input:
myMultiset1 = {1, 2, 2, 2};
myMultiset1 = {1, 1, 4, 5};

Output:
myStack: [ {1, 2, 2, 2};
                    {1, 1, 4, 5}; ]

Stack of Multisets in C++

To create a stack of multisets in C++, we will pass the template parameter in the stack declaration as a multiset. This will create a stack where each element is a multiset in itself.

Syntax to Declare Stack of Multiset

stack <multiset <Type>> myStack;

C++ Program to Create a Stack of Multisets

// C++ Program to illustrate how to create a stack of
// multisets
#include <iostream>
#include <set>
#include <stack>
using namespace std;

int main()
{
    // Initialize a multiset with some entries
    multiset<int> myMultiset1 = { 1, 2, 2 };
    multiset<int> myMultiset2 = { 1, 1, 2, 2 };

    // Create a stack of multisets
    stack<multiset<int> > myStack;
    myStack.push(myMultiset1);
    myStack.push(myMultiset2);

    // Print the stack of multisets
    while (!myStack.empty()) {
        multiset<int> topMultiset = myStack.top();
        myStack.pop();
        cout << "{";
        for (auto& elem : topMultiset) {
            cout << elem << ", ";
        }
        cout << "}, ";
    }
    cout << endl;

    return 0;
}

{1, 1, 2, 2, }, {1, 2, 2, }, 

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