#include <algorithm>
#include <cassert>
#include <iostream>
#include <iterator>
#include <vector>
 
using namespace std;

template < class BidirectionalIterator >
bool next_combination(BidirectionalIterator first1,
	BidirectionalIterator last1,
	BidirectionalIterator first2,
	BidirectionalIterator last2)
{
	if ((first1 == last1) || (first2 == last2)) {
		return false;
	}
	BidirectionalIterator m1 = last1;
	BidirectionalIterator m2 = last2; --m2;
	while (--m1 != first1 && !(*m1 < *m2)) {
	}
	bool result = (m1 == first1) && !(*first1 < *m2);
	if (!result) {
		while (first2 != m2 && !(*m1 < *first2)) {
			++first2;
		}
		first1 = m1;
		std::iter_swap(first1, first2);
		++first1;
		++first2;
	}
	if ((first1 != last1) && (first2 != last2)) {
		m1 = last1; m2 = first2;
		while ((m1 != first1) && (m2 != last2)) {
			std::iter_swap(--m1, m2);
			++m2;
		}
		std::reverse(first1, m1);
		std::reverse(first1, last1);
		std::reverse(m2, last2);
		std::reverse(first2, last2);
	}
	return !result;
}

template < class BidirectionalIterator >
bool next_combination(BidirectionalIterator first,
	BidirectionalIterator middle,
	BidirectionalIterator last)
{
	return next_combination(first, middle, middle, last);
}

int main() {
	vector<unsigned int> row{ 40, 40, 40, 50, 50, 60, 100 };
	vector<unsigned int>::iterator it = next(row.begin(), 3);

	do {
		copy(row.begin(), it, ostream_iterator<unsigned int>(cout, " "));
		cout << endl;
	} while(next_combination(row.begin(), it, row.end()));
}