Permutations without recursive function call

Question

Requirement: Algorithm to generate all possible combinations of a set , without duplicates , or recursively calling function to return results.

The majority , if not

Answer 1

A fairly simple C++ code without recursion.

#include 
#include 
#include 
#include 
#include 

// Integer data
void print_all_permutations(std::vector &data) {
    std::stable_sort(std::begin(data), std::end(data));
    do {
        std::copy(data.begin(), data.end(), std::ostream_iterator(std::cout, " ")), std::cout << '\n';
    } while (std::next_permutation(std::begin(data), std::end(data)));
}

// Character data (string)
void print_all_permutations(std::string &data) {
    std::stable_sort(std::begin(data), std::end(data));
    do {
        std::copy(data.begin(), data.end(), std::ostream_iterator(std::cout, " ")), std::cout << '\n';
    } while (std::next_permutation(std::begin(data), std::end(data)));
}

int main()
{
    std::vector v({1,2,3,4});
    print_all_permutations(v);

    std::string s("abcd");
    print_all_permutations(s);

    return 0;
}

We can find next permutation of a sequence in linear time.