Compilare: main.cpp: In function 'int main()': main.cpp:17:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < str.size(); i++) { ~~^~~~~~~~~~~~ main.cpp:21:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < str.size() && isalpha(str[i])) ~~^~~~~~~~~~~~ main.cpp:23:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < str.size() && isdigit(str[i])) ~~^~~~~~~~~~~~ main.cpp:29:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < str.size() && isdigit(str[i])) ~~^~~~~~~~~~~~