c - 如果语句为真，如何只显示 printf 语句？

Question

我正在做一个运费计算器，如果包裹重量超过 50 磅则无法运送包裹。我想只在包裹重量超过 50 磅时才显示声明，但无论如何它都会显示。

我把它当作 else 语句、if 语句和 if else 语句来试过。

main(){
    double distance, weight, weightCharges, shippingCharge, distanceCharge, unableToShip;
    printf ("Enter the weight of the package:\n");
    scanf ("%lf", &weight);
    printf ("Enter the distance your package needs to go: \n");
    scanf ("%lf", &distance);

    if (weight <= 10)
        weightCharges = weight * 3.00;
        else
            if (weight <= 50)
                weightCharges = weight * 5.00;
            else (weight > 50);
        weightCharges= 0;
    if (distance > 1000)
        distanceCharge = weightCharges + 10;
    shippingCharge = weightCharges + distanceCharge;
    unableToShip = weight > 50;

    printf ("Your total cost is: %.2lf \n", shippingCharge);
    printf ("We're unable to ship your package \n", unableToShip);

}

我希望第二个 printf 仅在我们无法运送他们的包裹时出现，但无论如何它都会出现。

Answer 1

if 在这里的工作方式与在其他任何地方的工作方式相同:

if (unableToShip) 
  printf ("We're unable to ship your package\n");