Compilare: user.cpp: In function ‘int main()’: user.cpp:21:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i<strlen(s)-1){ ^ user.cpp:24:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (j<strlen(s)-1){ ^ user.cpp:36:9: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (ok == 0) ^