Compilare: main.cpp: In member function 'void Trie::insert(std::__cxx11::string&, int, int)': main.cpp:42:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k == s.size()) { ~~^~~~~~~~~~~ main.cpp:47:23: warning: array subscript has type 'char' [-Wchar-subscripts] if (children[c] == NULL) { ^ main.cpp:48:23: warning: array subscript has type 'char' [-Wchar-subscripts] children[c] = new Trie(); ^ main.cpp:51:19: warning: array subscript has type 'char' [-Wchar-subscripts] children[c]->insert(s, k + 1, x); ^ main.cpp: In function 'bool f(int, std::vector<int>&)': main.cpp:61:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < q.size(); ++i) { ~~^~~~~~~~~~