Compilare: user.cpp: In function ‘int cb()’: user.cpp:85:8: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (i == 0) ^ user.cpp: In function ‘int main()’: user.cpp:95:32: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f, "%d%d\n", &r ,&c); ^ user.cpp:98:30: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(1 + a[i], M, f); ^