Compilare: main.cpp: In function 'int main()': main.cpp:27:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0; j<S.size(); j++) ~^~~~~~~~~ main.cpp:34:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k==S.size()) ~^~~~~~~~~~ main.cpp:53:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0; j<S.size(); j++) ~^~~~~~~~~