Compilare: user.cpp: In function ‘int main()’: user.cpp:15:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<=s.size();++i) ^ user.cpp:28:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<=s.size();++i) ^ user.cpp:30:15: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(isdigit(s[i])) ^ user.cpp:36:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<=s.size();++i) ^