/in/foo.cc: In function 'void fillStack(const string&, const std::map<char, int>&, std::vector<char>&)':
/in/foo.cc:36:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(auto i = 0; i < char_Que.size(); ++i) {
                     ~~^~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'char* caculation(const string&, std::map<char, int>&, std::stack<std::__cxx11::basic_string<char> >, const std::vector<char>&)':
/in/foo.cc:47:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(auto i = 0; i < char_Que.length(); ++i) {
                     ~~^~~~~~~~~~~~~~~~~~~
/in/foo.cc:56:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if(j < oper.size() && operlist[oper[j]] < operlist[oper[j+1]])
                ~~^~~~~~~~~~~~~
/in/foo.cc:58:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             else if(j < oper.size() && ((oper[j] == '-' || oper[j] == '/')  
                     ~~^~~~~~~~~~~~~
/in/foo.cc:62:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             else if(j < oper.size())
                     ~~^~~~~~~~~~~~~