Compilare: main.cpp: In function 'int main()': main.cpp:16:13: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 16 | while(i < s.size()){ | ~~^~~~~~~~~~ main.cpp:23:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 23 | while(j < s.size() && ((s[j] == ')' && st.top() == '(') || (s[j] == ']' && st.top() == '[') || (s[j] == '}' && st.top() == '{'))){ | ~~^~~~~~~~~~