If 语句给出不正确的输出

Question

这是我的代码：

if(weight<=5)
    cost=(2.8*weight);
if(weight<=20)
    cost=(2.8*5)+(5.2*(weight-5));
if(weight<=50)
    cost=(2.8*5)+(5.2*15)+(7*(weight-20));
if(weight>50)
    cost=(2.8*5)+(5.2*15)+(7*30)+(8.6*(weight-50));

当权重小于 6.9 时，为什么答案都是否定的？

Answer 1

在编写 IF 嵌套语句时，必须使用 ELSE 语句来防止出现这种情况。

正确的代码：

if(weight<=5) {
    cost=(2.8*weight);
} else if(weight<=20) {
    cost=(2.8*5)+(5.2*(weight-5));
} else if(weight<=50) {
    cost=(2.8*5)+(5.2*15)+(7*(weight-20));
} else if(weight>50) {
    cost=(2.8*5)+(5.2*15)+(7*30)+(8.6*(weight-50));
}

或者，您必须更好地定义范围，如下所示：

if(weight<=5) {
    cost=(2.8*weight);
} if(weight > 5 && weight<=20) {
    cost=(2.8*5)+(5.2*(weight-5));
} if(weight > 20 && weight<=50) {
    cost=(2.8*5)+(5.2*15)+(7*(weight-20));
} if(weight>50) {
    cost=(2.8*5)+(5.2*15)+(7*30)+(8.6*(weight-50));
}