Compilare: user.cpp: In function ‘int main()’: user.cpp:20:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < st.size()-1; i++) ^ user.cpp:28:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v.size() && ok; i++) ^ user.cpp:32:16: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (v[i] == ')') ^ user.cpp:35:16: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (v[i] == ']') ^