Compilare: main.cpp: In function 'void prefix()': main.cpp:13:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 13 | for(int i=1;i<s.size();i++) | ~^~~~~~~~~ main.cpp: In function 'int main()': main.cpp:30:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 30 | for(int i=a.size();i<s.size();i++) | ~^~~~~~~~~ main.cpp:31:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 31 | if(pi[i]==a.size()) | ~~~~~^~~~~~~~~~