Compilare: main.cpp: In function 'int main()': main.cpp:16:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i<strlen(b); i++) ~^~~~~~~~~~ main.cpp:20:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j<strlen(a) && ok; j++) ~^~~~~~~~~~