Compilare: main.cpp: In function 'void Insert(Trie*, std::__cxx11::string)': main.cpp:20:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'void Delete(Trie*, std::__cxx11::string)': main.cpp:38:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:43:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (p->children.size()>1 || (i!=s.size()-1 && p->num))//put 'last' to longest common prefix ~^~~~~~~~~~~~ main.cpp:54:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (last_index<s.size()) ~~~~~~~~~~^~~~~~~~~ main.cpp:57:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (last_index==s.size()-1) ~~~~~~~~~~^~~~~~~~~~~~ main.cpp: In function 'int Find(Trie*, std::__cxx11::string)': main.cpp:73:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'int LongestPrefix(Trie*, std::__cxx11::string)': main.cpp:96:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~