Compilare: main.cpp: In function 'int solve(int&)': main.cpp:18:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 18 | if( i < s.size() && s[i] == '(' ) { | ~~^~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:98:13: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 98 | while (i<s.size()) { | ~^~~~~~~~~ main.cpp:100:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 100 | if( i < s.size() && s[i] == '(' ) { | ~~^~~~~~~~~~ main.cpp:105:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 105 | while (i<s.size() && s[i] >= '0' && s[i] <= '9') { | ~^~~~~~~~~ main.cpp:136:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 136 | if(i < s.size() && s[i] != '(' && s[i] != ')') { | ~~^~~~~~~~~~