Compilare: user.cpp: In function ‘void prefix(std::string)’: user.cpp:21:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < s.size()) ^ user.cpp: In function ‘void prefix2(std::string)’: user.cpp:38:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < s.size()) ^ user.cpp: In function ‘int main()’: user.cpp:74:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (j < s.size()) ^ user.cpp:81:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (q == s2.size()) ^ user.cpp:91:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (j < s.size()) ^ user.cpp:98:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (q == s3.size()) ^ user.cpp:111:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < sol1.size(); i++) ^