makes combinations of vector elements

combo.cpp

#include <iostream>
#include <vector>
#include <cstdio>

template <typename T>
void combination(std::vector<T>& vec, std::vector<T>& tmp, int start, int end, int idx, int r);

int main() {
	std::vector<unsigned int> vec = {1,2,3,4,5};
	std::vector<unsigned int> tmp(vec.size());
	combination(vec, tmp, 0, vec.size() - 1, 0, 2);

	return 0;
}

template <typename T>
void combination(std::vector<T>& vec, std::vector<T>& tmp, int start, int end, int idx, int r) {
	if (r == idx) {
		for (int i = 0; i < r; i++) {
			std::cout << tmp[i] << " ";
		}
		std::cout << std::endl;
		return;
	}

	for (int i = start; i <= end && end-i+1 >= r - idx; i++) {
		tmp[idx] = vec[i];
		combination( vec , tmp , i+1 , end , idx+1 , r );
	}
}