Compilare: main.cpp: In member function 'void trie::add_string(std::__cxx11::string)': main.cpp:66:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<to_add.length(); i++) ~^~~~~~~~~~~~~~~~ main.cpp: In member function 'void trie::erase_string(std::__cxx11::string)': main.cpp:83:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<to_delete.length(); i++) ~^~~~~~~~~~~~~~~~~~~ main.cpp: In member function 'node* trie::get_root(std::__cxx11::string)': main.cpp:95:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<prefix.length(); i++) ~^~~~~~~~~~~~~~~~ main.cpp: In member function 'int trie::get_longest_common_prefix_of_string(std::__cxx11::string)': main.cpp:112:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<prefix.length(); i++) ~^~~~~~~~~~~~~~~~ main.cpp:111:13: warning: unused variable 'maxx' [-Wunused-variable] int maxx=0; ^~~~