Compilare: user.cpp:49:28: warning: multi-character character constant [-Wmultichar] sol += '3B'; ^ user.cpp: In function ‘bool make_sol(char)’: user.cpp:32:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (pointer < n && (pointer < sol.size() || last2)) { ^ user.cpp:33:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (pointer > sol.size()) { ^ user.cpp:49:25: warning: overflow in implicit constant conversion [-Woverflow] sol += '3B'; ^ user.cpp:62:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (sol.size() != n) ^