Compilare: main.cpp: In member function 'Trie::Node* Trie::insert_helper(Trie::Node*, std::__cxx11::string&, int, bool)': main.cpp:32:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(index < str.size()) ~~~~~~^~~~~~~~~~~~ main.cpp: In member function 'Trie::Node* Trie::and_insert_helper(Trie::Node*, std::__cxx11::string&, int, int)': main.cpp:50:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(index < str.size()) ~~~~~~^~~~~~~~~~~~ main.cpp: In member function 'void Trie::rec(Trie::Node*, int&)': main.cpp:65:18: warning: unused variable 'ch' [-Wunused-variable] char ch = 'a' + i; ^~ main.cpp: In function 'int main()': main.cpp:99:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a.size(); i++) ~~^~~~~~~~~~ main.cpp:101:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = a.size() - 1; j < a.size(); j++) ~~^~~~~~~~~~ main.cpp:113:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k = 0; k < a.size(); k++) ~~^~~~~~~~~~ main.cpp:114:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = a.size() - 1; j < a.size(); j++) ~~^~~~~~~~~~ main.cpp:137:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k = 0; k < b.size(); k++) ~~^~~~~~~~~~ main.cpp:138:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = k; j < b.size(); j++) ~~^~~~~~~~~~