all_strings.cpp

// generator.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <experimental\generator>
#include <string>
#include <numeric>
#include <vector>
#include <cstdint>
#include <sstream>
#include <iostream>
#include <utility>
#include <stack>

using namespace std;
using generator = experimental::generator<string>;
const string alphabet = "abcdefghijklmnopqrstuvwxyz";

generator all_strings()
{
	size_t set_size = 1;
	for (;; ++set_size) {
		stack<pair<string, size_t>> stack;
		stack.push(make_pair(string(""), set_size));
		do {
			const pair<string, size_t> p = stack.top();

			stack.pop();
			if (p.second == 0) {	
				co_yield p.first;
			}
			else {
				for (size_t i = 0; i < alphabet.size(); ++i) {
					string new_prefix = p.first + alphabet[i];
					stack.push(make_pair(new_prefix, p.second - 1));
				}
			}
		} while (!stack.empty());
	}
}

int main()
{
	for (auto p : all_strings()) {
		cout << p << endl;
	}
    return 0;
}