How to Delete Multiple Elements from a Set in C++?

In C++, sets are containers that store unique elements in some sorted order. In this article, we will learn how to delete multiple elements from a set using C++.

Example:

Input: 
set = {10, 20, 30, 40, 50, 60}
elements_to_delete = {20, 30, 40}

Output: 
Elements of set after deletion: 10 50 60

Removing Multiple Elements from a Set in C++

We can delete multiple elements from a set in C++ by passing each value to the std::set::erase() member function of the std::set class. We can use the loop for deleting multiple values.

C++ Program to Delete Multiple Elements from a Set

The below example demonstrates how we can use erase() function to delete multiple elements from a set in C++ STL.

C++

// C++ Program to illustrate how to delete multiple elements
// from a set
#include <iostream>
#include <set>
using namespace std;

int main()
{
    // Set and elements to be deleted from a set
    set<int> s = { 10, 20, 30, 40, 50, 60 };
    set<int> elements_to_delete = { 20, 30, 40 };

    // Print the original set
    cout << "Original set: ";
    for (auto it = s.begin(); it != s.end(); ++it)
        cout << *it << " ";
    cout << endl;

    // Delete elements from the set
    for (auto it = elements_to_delete.begin();
         it != elements_to_delete.end(); ++it)
        s.erase(*it);

    // Print the set after deletion
    cout << "Set after deletion: ";
    for (auto it = s.begin(); it != s.end(); ++it)
        cout << *it << " ";
    cout << endl;

    return 0;
}

Output

Original set: 10 20 30 40 50 60 
Set after deletion: 10 50 60 

Time Complexity: O(K log N), here K is the number of elements to delete and N is the size of the original set.
Auxilliary Space: O(N)