Given two strings, determine if they share a common substring. A substring may be as small as one character.

issubstring.cpp

string twoStrings(string s1, string s2) {
 
    set<char> f(s1.begin(), s1.end());
            std::cout  << s1 << "\n" << s2 << "\n\n";

    for(auto i : s2){
        std::cout << i << "\n";

       auto ret = f.insert(i);
       if(ret.second == false){
           std::cout << i << "  here\n";
          return "YES";
       }else {
           f.erase(i);
       }
       
    }
    return "NO";
}