#include <array>
#include <iostream>
 
template <std::size_t N>
bool increase(std::array<std::size_t, N>& a, std::size_t base)
{
    for (auto rit = a.rbegin(); rit != a.rend(); ++rit) {
        ++*rit;
        if (*rit != base) {
            return true;
        }
        *rit = 0;
    }
    return false;
}
 
template <std::size_t N>
void print(std::array<std::size_t, N>& a, const char* symbols)
{
    for (auto e : a) {
        std::cout << symbols[e];
    }
    std::cout << std::endl;
}
 
 
int main()
{
    const char symbols[] = "abcde";
    std::array<std::size_t, 3> a{0};
 
    do
    {
        print(a, symbols);
    } while (increase(a, 5));
    return 0;
}
 

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