Compilare: main.cpp: In function 'void insert_word(std::__cxx11::string)': main.cpp:29:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'void delete_word(std::__cxx11::string)': main.cpp:46:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'int find_word(std::__cxx11::string)': main.cpp:59:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'int longest_prefix(std::__cxx11::string)': main.cpp:76:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~