Compilare: main.cpp: In function 'void insertie(std::__cxx11::string)': main.cpp:18:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.length(); ++i) { ~~^~~~~~~~~~~~ main.cpp: In function 'bool deleter(node*&, char*)': main.cpp:30:91: warning: converting to non-pointer type 'long int' from NULL [-Wconversion-null] (deleter(leaf->copii[int(word[0] - 'a')], word + 1)) ? leaf->numberOfChildren-- : NULL; ^~~~ main.cpp: In function 'int howManyTimes(std::__cxx11::string)': main.cpp:44:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.length(); ++i) { ~~^~~~~~~~~~~~ main.cpp: In function 'int longestPrefix(std::__cxx11::string)': main.cpp:55:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.length(); ++i) { ~~^~~~~~~~~~~~