Compilare: main.cpp: In function 'void add_elements(std::stack<char>&, std::string)': main.cpp:82:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 82 | for(int i = 0; i < str.size(); i++){ | ~~^~~~~~~~~~~~ main.cpp: In function 'void solution(std::string, std::stack<char>, std::string&, int&, bool)': main.cpp:89:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 89 | for(int i = 0; i < in_string.size(); i++) { | ~~^~~~~~~~~~~~~~~~~~