Compilare: user.cpp: In function ‘void remove()’: user.cpp:31:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0;i < v[j].size();i++) ^ user.cpp: In function ‘int search()’: user.cpp:42:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0;i < v[j].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:58:6: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (op == 3) ^