Compilare: user.cpp: In function ‘int main()’: user.cpp:21:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0; i<strlen(s); i++){ ^ user.cpp:23:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=i+1; j<strlen(s)-1; j++) ^ user.cpp:30:9: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (ok == 0) ^