Compilare: user.cpp: In function ‘void add_word(trie_node*, std::string, int)’: user.cpp:24:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i==word.length()) {current->nr++; return;} ^ user.cpp: In function ‘bool delete_word(trie_node*, std::string, int)’: user.cpp:39:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i==word.length()) current->nr--; ^ user.cpp: In function ‘int search_word(trie_node*, std::string, int)’: user.cpp:54:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i==word.length()) return current->nr; ^