Decimal to hex :-
std::stringstream ss;
ss<< std::hex << decimal_value; // int decimal_value
std::string res ( ss.str() );
std::cout << res;
Hex to decimal :-
std::stringstream ss;
ss << hex_value ; // std::string hex_value
ss >> std::hex >> decimal_value ; //int decimal_value
std::cout << decimal_value ;
Ref: std::hex
, std::stringstream