Standard Template Library II - Set - 2020

Sets and multisets sort their elements automatically. Sets do not allow duplicates while multisets allow duplicates.

#include <iostream>
#include <set>

using namespace std;

struct Compare
{
    bool operator()(const int &a;, const int &b;) const
    {
        return a % 10 < b % 10;
    }
};

int main()
{
    const int a[] = {8, 2, 24, 9, 7, 3, 4, 6, 15, 2};
    const int count = sizeof(a) / sizeof(a[0]);
    for(int i = 0; i < count; i++)
	cout << a[i] << " ";
    cout << endl;

    set<int> s(a, a + count); 
    set<int>::iterator it;
    for(it = s.begin(); it != s.end(); ++it)
	cout << *it << " ";
    cout << endl;

    set<int, Compare>::iterator sit;
    set<int, Compare> new_s(s.begin(), s.end());
    for(sit = new_s.begin(); sit != new_s.end(); ++sit)
	cout << *sit << " ";
    return 0;
}

Output:

8 2 24 9 7 3 4 6 15 2
2 3 4 6 7 8 9 15 24
2 3 4 15 6 7 8 9

As we see from the output of the second line, set srots its element automatically and removes any duplicates. The third line was sorted with the last digits.