Compilare: user.cpp: In function ‘std::vector<int>::iterator find_val(int)’: user.cpp:13:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<Hash[val].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:37:11: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(op==3) ^