Compilare: user.cpp: In function ‘bool f(std::string, std::string)’: user.cpp:13:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a.length(); ++i) ^ user.cpp:17:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(p>b.length()) return 0; ^ user.cpp: In function ‘int main()’: user.cpp:29:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(v[i].length() > m) m=v[i].length(),u=i; ^ user.cpp:30:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(v[i].length()==m && v[i] < v[u]) u=i; ^