#include <iostream>
#include <string>
#include <stdlib.h>
#include "Language.h"

int main(int argc, char **argv) {

if (--argc < 2) {
    std::cout << "Usage: chains REGEX LENGTH" << std::endl;
    return 1;
}

Language lang(argv[1]);
lang.GenerateWords(atoi(argv[2]));

return 0;
}

#include <iostream>
#include <cctype>
#include "Language.h"

using namespace std;

static string word;

Language::Language(string reg)
{
this->reg = regex(reg);

for (int i = 0; i < reg.length(); i++)
    if (isalpha(reg[i]))
            alphabet.insert(reg[i]);
}

Language::Language(string alphabet, string reg)
{
this->reg = regex(reg);

for (int i = 0; i< alphabet.length(); i++)
    this->alphabet.insert(alphabet[i]);
}

void Language::_GenerateWords(int i)
{
for (auto& letter : alphabet) {
    word[i] = letter;
    if (i < word.length() - 1)
        _GenerateWords(i+1);
    else if (regex_match(word, reg))
        cout << word << endl;
}
}

void Language::GenerateWords(int length)
{
word = string(length, *(alphabet.begin()));

_GenerateWords(0);
}

#include <regex>
#include <set>

class Language {
std::set<char> alphabet;
std::regex reg;

void _GenerateWords(int);

public:
Language(std::string);
Language(std::string, std::string);
void GenerateWords(int = 1);
};