gistfile1.txt

#include <iostream>
#include <string>

template< class ForwardIt1, class ForwardIt2 >
bool is_subset(ForwardIt1 first1, ForwardIt1 last1,
               ForwardIt2 first2, ForwardIt2 last2)
{
    auto initial = first2;
    
    for (; (first1 != last1) && (first2 != last2); ++first1)
    {
        if (*first1 != *first2)
            first2 = initial;
        else
            ++first2;
    }
    
    return first2 == last2;
}

int main()
{
    std::string x("abcheloxyz"), y("z");
    
    std::cout << std::boolalpha;
    std::cout << is_subset(x.begin(), x.end(),
                           y.begin(), y.end());
}