Compilare: user.cpp: In function ‘void last_lee()’: user.cpp:44:16: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (is_ok_two(x + d_x[k], y + d_y[k])) ^ user.cpp: In function ‘void set_first()’: user.cpp:76:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < x.size(); ++j) { ^