Compilare: main.cpp: In function 'void adaug(nod*&, std::__cxx11::string)': main.cpp:22:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); i++) ~^~~~~~~~~ main.cpp:28:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=i; j<s.size(); j++) ~^~~~~~~~~ main.cpp: In function 'void scoate(nod*&, std::__cxx11::string)': main.cpp:50:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); i++) ~^~~~~~~~~ main.cpp: In function 'void afiseaza(nod*&, std::__cxx11::string)': main.cpp:73:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); i++) ~^~~~~~~~~ main.cpp: In function 'void prefix(nod*&, std::__cxx11::string)': main.cpp:81:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); i++) ~^~~~~~~~~