Compilare: user.cpp: In function ‘void compute_prefix(const string&)’: user.cpp:21:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < s.length(); i++) ^ user.cpp: In function ‘int count_matches(const string&, const string&)’: user.cpp:54:50: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = len = kmp_prefix[len]; j < p.size(); j++) ^ user.cpp:65:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (len == p.size()) ^ user.cpp: In function ‘int main()’: user.cpp:84:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < pos.size(); i++) ^