CodeWars/4kyu/permutations/solution.cpp

#include <algorithm>
#include <iostream>
#include <set>
#include <string>
#include <vector>

template <typename T> bool nextPermutation(std::vector<T> &vec) {
    // Find non-increasing suffix
    if (vec.empty())
        return false;
    typename std::vector<T>::iterator i = vec.end() - 1;
    while (i > vec.begin() && *(i - 1) >= *i)
        --i;
    if (i == vec.begin())
        return false;

    // Find successor to pivot
    typename std::vector<T>::iterator j = vec.end() - 1;
    while (*j <= *(i - 1))
        --j;
    std::iter_swap(i - 1, j);

    // Reverse suffix
    std::reverse(i, vec.end());
    return true;
}

std::vector<std::string> permutations(std::string s) {
    std::set<std::string> strings;
    std::vector<std::string> result;
    std::vector<char> s_vec;

    // copy string into vector

    for (auto ch = s.begin(); ch != s.end(); ch++) {
        s_vec.push_back(*ch);
    }

    // do the magic
    std::sort(s_vec.begin(), s_vec.end());
    do {
        strings.insert(std::string(s_vec.begin(), s_vec.end()));
    } while (nextPermutation(s_vec));

    std::copy(strings.begin(), strings.end(), std::back_inserter(result));
    return result;
}