Compilare: main.cpp: In function 'void add(std::__cxx11::string)': main.cpp:20:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ~~^~~~~~~~~~ main.cpp: In function 'void erase(std::__cxx11::string)': main.cpp:31:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ~~^~~~~~~~~~ main.cpp: In function 'int query1(std::__cxx11::string)': main.cpp:45:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ~~^~~~~~~~~~ main.cpp: In function 'int query2(std::__cxx11::string)': main.cpp:54:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ~~^~~~~~~~~~