Compilare: user.cpp: In function ‘void preprocess(std::string&)’: user.cpp:15:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < w.size()) { ^ user.cpp: In function ‘void search(std::string&, std::string&)’: user.cpp:24:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < s.size()) { ^ user.cpp:27:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (j == w.size()) { ^ user.cpp: In function ‘int main()’: user.cpp:44:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < result.size(); ++i) { ^