bfe.cpp

#include <fstream>
#include <functional>
#include <thread>
#include <memory>
#include <iostream>

int main(){
    std::ofstream ofile("bfe.hpp");
    std::size_t size = 5;
    const char pattern_array[] = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '_' };
    std::unique_ptr<char[]> buffer(new char[size + 1]);
    std::function<void(int, int, char*, char*)> f = [&](int s, int depth, char *p, char *q){
        if(depth == 0){
            *(q + 1) = '\0';
            for(std::size_t i = 0; i < sizeof(pattern_array); ++i){
                *q = pattern_array[i];
                ofile << p << ",\n";
            }
        }else{
            for(std::size_t i = 0; i < sizeof(pattern_array); ++i){
                if(depth == s && i > 25){ break; }
                *q = pattern_array[i];
                f(s, depth - 1, p, q + 1);
            }
        }
    };
    for(std::size_t i = 1; i <= size; ++i){
        f(i - 1, i - 1, buffer.get(), buffer.get());
    }
    return 0;
}