All permutations of length k from n characters with repetition in CPP

Question

I would like to know if there is already an implementation in CPP to find all permutations of n characters of length k(1,2,3,4 etc) with repetitions. I hope there is but i c

Answer 1

This solution works out for all standard container and also static arrays. I think this can be used also for classes and structures

#include 
#include 
#include 
#include 
#include 
#include 

template
bool nextPermutationWithRepetition(InputIt begin, InputIt end, T from_value, T to_value) {
    auto it = std::find_if_not(std::make_reverse_iterator(end),
                               std::make_reverse_iterator(begin),
                               [&to_value](auto current) { return to_value == current; });

    if (it == std::make_reverse_iterator(begin))
        return false;

    auto bound_element_iterator = std::prev(it.base());

    (*bound_element_iterator)++;
    std::fill(std::next(bound_element_iterator), end, from_value);

    return true;
}

int main() {
    std::list vec(3, 0);

    do {
        std::copy(vec.begin(), vec.end(), std::ostream_iterator(std::cout, " "));
        std::cout << std::endl;
    } while (nextPermutationWithRepetition(vec.begin(), vec.end(), 0, 2));

    return  0;
}