折扣码..我哪里出错了？

Question

This code is designed to give the final price of an item based off of the customers quantity. I have already added in the equations but when it is ran it the discount and the final price are not evaluating correctly. If someone knows where I went wrong in the pseudocode, it would be very helpful.

using namespace std;
int main() {

    // Variables
    double Retail, quantity, discount1, discount2, discount3, discount4, TotalCost1, TotalCost2, TotalCost3, TotalCost4;
    Retail = 99;
    quantity = 0;
    discount1 = (quantity * Retail) * .20;
    discount2 = (quantity * Retail) * .30;
    discount3 = (quantity * Retail) * .40;
    discount4 = (quantity * Retail) * .50;
    TotalCost1 = quantity - discount1;
    TotalCost2 = quantity - discount2;
    TotalCost3 = quantity - discount3;
    TotalCost4 = quantity - discount4;

    //Equations
    cout << "Please enter the quantity of items you would like to purchase: " << endl;
    cin >> quantity;
    cout << "The number of items being purchased is: " << quantity << endl;

    if (quantity <= 19) {
        cout << "Your final price is: " << discount1 << endl;
    }
    if (quantity >= 20) {
        cout << "Your final price is: " << discount2 << endl;
    }
    if (quantity >= 50) {
        cout << "Your final price is: " << discount3 << endl;
    }
    if (quantity >= 100) {
        cout << "Your final price is: " << discount4 << endl;
    }




        system("pause");
}

Answer 1

Is it just that you're quantity isn't defined as being anything except 0 before your calculate the discounts? I moved the read of your purchase before the calculations and got better results (using online compiler).

double Retail, quantity, discount1, discount2, discount3, discount4, TotalCost1, TotalCost2, TotalCost3, TotalCost4;
Retail = 99;
quantity = 0;

//Equations
cout << "Please enter the quantity of items you would like to purchase: " << endl;
cin >> quantity;
cout << "The number of items being purchased is: " << quantity << endl;

discount1 = (quantity * Retail) * .20;
discount2 = (quantity * Retail) * .30;
discount3 = (quantity * Retail) * .40;
discount4 = (quantity * Retail) * .50;
TotalCost1 = quantity - discount1;
TotalCost2 = quantity - discount2;
TotalCost3 = quantity - discount3;
TotalCost4 = quantity - discount4;


if (quantity <= 19) {
    cout << "Your final price is: " << discount1 << endl;
}
if (quantity >= 20) {
    cout << "Your final price is: " << discount2 << endl;
}
if (quantity >= 50) {
    cout << "Your final price is: " << discount3 << endl;
}
if (quantity >= 100) {
    cout << "Your final price is: " << discount4 << endl;
}


Please enter the quantity of items you would like to purchase: 
The number of items being purchased is: 19
Your final price is: 376.2