Gas cost calculator

I am refreshing my university knowledge on C++ due to a job interview and I am trying to understand everything in depth. Is there any reason for me to use pointers and dynamic memory features of C++ in this example?

It's not that clear to me when should I use these features.

#include 

using namespace std;

int main(){

  const int range = 100; // Consumption is lt/100km
  double * km = new double;
  double * consumption = new double;
  double * gas_price = new double;
  double * gas_cost = new double;

  cout  Enter distance in km: ";
  cin >> *km;
  cout  Enter consumption (l/100km): ";
  cin >> *consumption;
  cout  Enter gas price in euros: ";
  cin >> *gas_price;

  *gas_cost = *consumption * *gas_price * *km /range ;

  cout  Gas cost: [" << *gas_cost << "€]";
  cout << endl;

}

In this minimal of an example, I would not use pointers or dynamic memory features.

As I read this code, I am more concerned about the fact that the code is not divided into logical functions instead of having main handle everything and that you are using namespace std;.

You should not use using namespace std; in your code, but rather specify which namespace you are using like this: std::cout. If you do use this, it can cause many problems.

You should also not have main handle all the work. You could, for example, have a method to calculate the gas cost, and pass it any required parameters.

Additionally, I would probably just initialize the values with -1.

double consumption = -1;
do {
    std::cout  Enter consumption (l/100km): ";
    std::cin >> consumption;

    if (!std::cin) {
        std::cin.clear();
        std::string s = "";
        getline(std::cin, s);
    }
while (consumption > 100 || consumtion < 1);

This will validate the consumption input, and also not let your program crash if the user inputs a string.

Validation is very important if your program expects input with certain specifications (in this case, it both expects a double and a value with a specific range).

StackExchange Code Review Q#82304, answer score: 5