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Field Guide

Change Calculator

Try converting the most recent version of your change calculator to C/C++. The logic of the program should remain the same, the syntax will just look a little different.

The change of library does mean that you cannot use C#‘s ToInt32 method. However, C provides an equivalent called stoi which also converts text to an integer. This works just like ToInt32, so you can replace that code with stoi, and it should work as it did before.

Have a go yourself.

  • /*
    * Program: Simple Change
    * Calculate the ideal change for a given transaction.
    */
    

    #include "splashkit.h"
    

    using std::stoi;
    using std::to_string;
    

    int main()
    {
        const int NUM_COIN_TYPES = 6;
    

        const int TWO_DOLLARS = 200;
        const int ONE_DOLLAR = 100;
        const int FIFTY_CENTS = 50;
        const int TWENTY_CENTS = 20;
        const int TEN_CENTS = 10;
        const int FIVE_CENTS = 5;
    

        string again = ""; // used to check if the user want to run again
        string line;
        int to_give;
        int coin_value;
        string coin_text;
    

        do
        {
            write("Cost of item in cents: ");
            line = read_line();
            while (!is_integer(line))
            {
                write_line("Please enter a whole number.");
                write("Cost of item in cents: ");
                line = read_line();
            }
            int cost_of_item = stoi(line);
    

            write("Payment in cents: ");
            line = read_line();
            while (!is_integer(line))
            {
                write_line("Please enter a whole number.");
                write("Payment in cents: ");
                line = read_line();
            }
    

            int amount_paid = stoi(line);
    

            int change_value = amount_paid - cost_of_item;
    

            if (change_value < 0)
            {
                write_line("Not enough money was paid.");
                write("Run again: ");
                again = read_line();
                continue;
            }
    

            write_line("Change to give " + to_string(change_value));
    

            write("Change: ");
    

            for (int i = 0; i < NUM_COIN_TYPES; i++)
            {
                switch (i)
                {
                case 0:
                    coin_value = TWO_DOLLARS;
                    coin_text = "$2, ";
                    break;
                case 1:
                    coin_value = ONE_DOLLAR;
                    coin_text = "$1, ";
                    break;
                case 2:
                    coin_value = FIFTY_CENTS;
                    coin_text = "50c, ";
                    break;
                case 3:
                    coin_value = TWENTY_CENTS;
                    coin_text = "20c, ";
                    break;
                case 4:
                    coin_value = TEN_CENTS;
                    coin_text = "10c, ";
                    break;
                case 5:
                    coin_value = FIVE_CENTS;
                    coin_text = "5c";
                    break;
                default:
                    coin_value = 0;
                    coin_text = "ERROR";
                    break;
                }
    

                // Give Change
                to_give = change_value / coin_value;
                change_value = change_value - to_give * coin_value;
                write(to_string(to_give) + " x " + coin_text);
            }
    

            write_line();
            write("Run again: ");
            again = read_line();
        } while (again != "n" && again != "N");
    }