Compilare: user.cpp: In function ‘bool cmp(const string&, const string&)’: user.cpp:21:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size() && i < b.size(); i++) ^ user.cpp:21:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size() && i < b.size(); i++) ^ user.cpp: In function ‘void backtr(int, int)’: user.cpp:53:124: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if (order[lin] == 1 || !cmp(order_type[order[lin] - 1] ? col_nr[order[lin] - 1] : lin_nr[order[lin] - 1], lin_nr[lin]) && !cmp(order_type[order[lin] - 1] ? col_nr[order[lin] - 1] : lin_nr[order[lin] - 1], col_nr[col])) { ^ user.cpp:66:124: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if (order[lin] == 1 || !cmp(order_type[order[lin] - 1] ? col_nr[order[lin] - 1] : lin_nr[order[lin] - 1], lin_nr[lin]) && !cmp(order_type[order[lin] - 1] ? col_nr[order[lin] - 1] : lin_nr[order[lin] - 1], col_nr[col])) { ^