Compilare: user.cpp: In function ‘void a_precalc()’: user.cpp:21:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(; j < a.size(); j++) ^ user.cpp: In function ‘void str_match()’: user.cpp:59:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j < b.size()) ^ user.cpp:69:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i == a.size()) ^