Compilare: main.cpp: In member function 'void trie::add_string(const 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(const string&)': main.cpp:84:23: 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(const string&)': main.cpp:96:23: 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(const string&)': main.cpp:113:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<prefix.length(); i++) ~^~~~~~~~~~~~~~~~ main.cpp:112:13: warning: unused variable 'maxx' [-Wunused-variable] int maxx=0; ^~~~ main.cpp: In function 'int main()': main.cpp:137:9: warning: unused variable 'a' [-Wunused-variable] int a,b; ^ main.cpp:137:11: warning: unused variable 'b' [-Wunused-variable] int a,b; ^