Compilare: main.cpp: In function 'void prefix_function()': main.cpp:12:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 12 | for(int i=1;i<S.size();i++) | ~^~~~~~~~~ main.cpp: In function 'int main()': main.cpp:27:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 27 | for(int i=0;i<S.size();i++) | ~^~~~~~~~~ main.cpp:28:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 28 | if(pi[i]==A.size()) | ~~~~~^~~~~~~~~~