Compilare: main.cpp: In member function 'void Trie::insert(std::__cxx11::string, int)': main.cpp:41:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (s.size() == k) { ~~~~~~~~~^~~~ main.cpp:48:23: warning: array subscript has type 'char' [-Wchar-subscripts] if (children[c] == NULL) { ^ main.cpp:49:23: warning: array subscript has type 'char' [-Wchar-subscripts] children[c] = new Trie(); ^ main.cpp:52:19: warning: array subscript has type 'char' [-Wchar-subscripts] children[c]->insert(s, k + 1); ^ main.cpp: In member function 'bool Trie::contains(std::__cxx11::string, int)': main.cpp:56:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (s.size() == k) { ~~~~~~~~~^~~~ main.cpp:62:23: warning: array subscript has type 'char' [-Wchar-subscripts] if (children[c] == NULL) { ^ main.cpp:66:26: warning: array subscript has type 'char' [-Wchar-subscripts] return children[c]->contains(s, k + 1); ^