Compilare: user.cpp: In function ‘void update(std::string, int, Node*)’: user.cpp:23:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(pos == s.length()) ^ user.cpp:28:9: warning: unused variable ‘y’ [-Wunused-variable] int y = s[pos] - 'a'; ^ user.cpp: In function ‘bool del(std::string, int, Node*)’: user.cpp:40:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(pos == s.length()) ^ user.cpp: In function ‘int queryAp(std::string, int, Node*)’: user.cpp:64:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(pos == s.length()) ^