Compilare: user.cpp: In function ‘int main()’: user.cpp:19:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0;i < s.length();++i) ~~^~~~~~~~~~~~ user.cpp:46:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0;i < s.length();++i) ~~^~~~~~~~~~~~ user.cpp:70:4: warning: ‘sign’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (sign == false) ^~ user.cpp:40:4: warning: ‘sign’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (sign == false) ^~