/*
VIM: let b:cf5build="clang++ -std=c++20 -O2 -pthread -I. {SRC} -o {OUT}"
VIM: let b:cf5run="{OUT}"
*/
#include <iostream>
#include <exception>
#include <chrono>

void permutate(auto b, auto e)
{
    auto bt = std::reverse_iterator(e);
    auto et = std::reverse_iterator(b);

    auto it = bt+1;
    for ( ; it != et && *it >= *(it-1); ++it);

    for (auto qt = bt, rt = it-1; rt > qt; qt++, rt--){
        std::swap(*qt, *rt);
    }

    if (it != et){
        auto pt = it-1;
        for( ; pt != bt && *it >= *pt; --pt);
        std::swap(*it, *pt);
    }
}

void test(std::string char_set)
{
    std::sort(char_set.begin(), char_set.end());
    std::string perm = char_set;
    int i = 0;
    do {
        ++i;
        std::cout << perm << '\n';
        permutate(perm.begin(), perm.end());
    } while (perm != char_set);

    std::cout << i << '\n' << "-------------------------------------\n";
}

int main ( void )
{try{
    auto begin = std::chrono::high_resolution_clock::now();

    test( "abcd" );
    test( "aab" );
    test( "aabb" );
    test( "aaabbb" );

    //......

    auto end = std::chrono::high_resolution_clock::now();
    std::chrono::duration<double> seconds = end - begin;
    std::cout << "Time: " << seconds.count() << std::endl;
    return 0;
}
catch ( const std::exception& e )
{
    std::cerr << std::endl
            << "std::exception(\"" << e.what() << "\")." << std::endl;
    return 2;
}
catch ( ... )
{
    std::cerr  << std::endl
            << "unknown exception." << std::endl;
    return 1;
}}