Compilare: main.cpp: In function 'void insert(std::__cxx11::string, trie*)': main.cpp:26:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'int apare(std::__cxx11::string, trie*)': main.cpp:39:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'int pref(std::__cxx11::string, trie*)': main.cpp:51:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'bool sterge(std::__cxx11::string, int, trie*)': main.cpp:63:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (l==s.size()) ~^~~~~~~~~~ main.cpp:76:1: warning: control reaches end of non-void function [-Wreturn-type] } ^