Compilare: user.cpp: In function ‘int main()’: user.cpp:31:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 1; i<s.size(); i++) ^ user.cpp:64:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i == s.size()-1) ^ user.cpp:77:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 1; i<s.size(); i++) ^ user.cpp:93:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i<s.size(); i++) ^ user.cpp:22:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j; ^