Compilare: user.cpp: In function ‘bool cmp(std::string, std::string)’: user.cpp:11:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < a.size() && j < b.size()) ^ user.cpp:11:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < a.size() && j < b.size()) ^ user.cpp:15:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i == a.size()) return 1; ^ user.cpp: In function ‘int main()’: user.cpp:37:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (a[i].size() == l) return cout << a[i], 0; ^