class Solution { public: string toHexspeak(string num) { stringstream ss; Long Long Inter; // turn hex String hexret; ss << num; ss >> inter; ss.clear(); ss << hex << inter; SS >> hexret; // Get conversion relationship Map < char , char > Transform = { {'a','A'}, {'b','B'}, {'c','C'}, {'d','D'}, { ' And ' , ' E ' }, {'f','F'}, {'1','I'}, { ' 0 ' , ' The ' } }; for(int i = 0; i < hexret.size(); ++i){ if(transform.count(hexret[i]) == 0){ return "ERROR"; } hexret[i] = transform[hexret[i]]; } return hexret; } };