Compilare: main.cpp: In function 'bool pos(std::vector<char>, int)': main.cpp:14:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k == ss.size() && s.size() == 0) return 1; ~~^~~~~~~~~~~~ main.cpp:21:31: warning: array subscript has type 'char' [-Wchar-subscripts] else for(auto c : str[s[0]]) { ^ main.cpp: In function 'int main()': main.cpp:47:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 2; i < a.size(); i += 2) { ~~^~~~~~~~~~