C++ Using STL Multiset Program

Hello Everyone!

In this tutorial, we will learn about the working of Multiset in STL and its implementation in the C++ programming language.

What is a Set?

In programming, a Set is used to store unique values of a list and also automatically providing an ordering to it's elements. By default, the ordering is in the ascending order.

The elements are inserted using the insert() method. If the same value is inserted multiple times, the set automatically deletes the duplicates and only store the single copy of that element.

The elements of the Set are deleted using the erase() method.

The erase(s.begin(),s.find(x)) method deletes all the elements of the set from beginning to less than x.

What is a Multiset?

Multisets are similar to set, with an exception that multiple elements can have same values (duplicates are retained).

For better understanding of it's implementation, refer to the well commented C++ code given below.

Code:

#include <iostream>
#include <bits/stdc++.h>

using namespace std;

//Function to print the elements of the multiset using an iterator
void show(multiset<int> s)
{
    //declaring an iterator to iterate through the multiset
    multiset<int>::iterator i;

    for (i = s.begin(); i != s.end(); i++)
    {
        cout << *i << "  "; //accessing the elements of the multiset using * as i stores the address to each element
    }

    cout << endl;
}

int main()
{
    cout << "\n\nWelcome to Studytonight :-)\n\n\n";
    cout << " =====  Program to demonstrate the working of a Multiset, in CPP  ===== \n\n\n\n";

    cout << "*** Multisets are similar to set, with an exception that multiple elements can have same values. *** \n\n";

    //Set declaration (Set of integers)
    multiset<int> s;

    //Filling the elements by using the insert() method.
    cout << "\n\nFilling the Multiset with integers in random order."; //Multiset automatically stores them in order

    s.insert(5);
    s.insert(39);
    s.insert(5);
    s.insert(82);
    s.insert(39);
    s.insert(54);

    cout << "\n\nThe number of elements in the Multiset are: " << s.size();

    cout << "\n\nThe elements of the Multiset are: ";
    show(s);

    multiset<int>::iterator it;

    //Deleting all the elements of the set that are less than 54
    s.erase(s.begin(), s.find(54));

    cout << "\n\nAfter deleting all the elements that are less than 54, the Multiset becomes : ";

    for (it = s.begin(); it != s.end(); it++)
    {
        cout << " " << *it;
    }

    cout << "\n\n\n";

    return 0;
}

Output:

We hope that this post helped you develop a better understanding of the concept of Multiset in STL and its implementation in C++. For any query, feel free to reach out to us via the comments section down below.

Keep Learning : )