The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference, 2nd Edition
by Nicolai M. Josuttis, Addison Wesley Longman, 2012
Copyright © 2012 by Pearson Education, Inc. and Nicolai M. Josuttis
#include <set>
#include <algorithm>
#include <iterator>
#include <iostream>
using namespace std;
int main()
{
// unordered set with elements from 1 to 9
set<int> coll = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
// print all elements of the collection
copy (coll.cbegin(), coll.cend(),
ostream_iterator<int>(cout," "));
cout << endl;
// Remove all elements with value 3
// - algorithm remove() does not work
// - instead member function erase() works
int num = coll.erase(3);
// print number of removed elements
cout << "number of removed elements: " << num << endl;
// print all elements of the modified collection
copy (coll.cbegin(), coll.cend(),
ostream_iterator<int>(cout," "));
cout << endl;
}