Compilare: main.cpp: In function 'std::__cxx11::string Add(std::__cxx11::string, std::__cxx11::string)': main.cpp:20:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0, r = 0; i < x.size() && i < y.size(); ++i, r /= 10) ~~^~~~~~~~~~ main.cpp:20:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0, r = 0; i < x.size() && i < y.size(); ++i, r /= 10) ~~^~~~~~~~~~ main.cpp:25:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < x.size()) ~~^~~~~~~~~~ main.cpp:31:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < y.size()) ~~^~~~~~~~~~ main.cpp: In function 'int Compare(std::__cxx11::string, std::__cxx11::string)': main.cpp:53:10: warning: unused variable 'val' [-Wunused-variable] bool val; ^~~ main.cpp: In function 'std::__cxx11::string Plus(std::__cxx11::string, std::__cxx11::string)': main.cpp:88:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = -i; j < y.size(); ++j) ~~^~~~~~~~~~ main.cpp:100:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = y.size(); j < aux.size(); ++j) ~~^~~~~~~~~~~~ main.cpp:118:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = i; j < x.size() && j < aux.size(); ++j) ~~^~~~~~~~~~ main.cpp:118:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = i; j < x.size() && j < aux.size(); ++j) ~~^~~~~~~~~~~~ main.cpp:130:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = x.size(); j < aux.size(); ++j) ~~^~~~~~~~~~~~ main.cpp:132:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = aux.size(); j < x.size(); ++j) ~~^~~~~~~~~~