Compilare: user.cpp: In function ‘int main()’: user.cpp:40:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < S.length()-1; i++) ^ user.cpp:48:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < S1.length(); i++) ^ user.cpp:56:41: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if (!st.empty() && (st.top() == '(' && S1[i] == ')' || st.top() == '[' && S1[i] == ']')) ^