Compilare: main.cpp: In function 'void insert_word(std::__cxx11::string)': main.cpp:35:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'void delete_word(std::__cxx11::string)': main.cpp:53:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:63:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i==s.size()) ~^~~~~~~~~~ main.cpp:67:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i++;i<=s.size();i++) ~^~~~~~~~~~ main.cpp:70:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i==s.size()) ~^~~~~~~~~~ main.cpp: In function 'int find_word(std::__cxx11::string)': main.cpp:88:19: 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:105:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~