ABC邮购杂货店出售的洋蓟售价为2.05美元/磅，甜菜售价为1.15美元/磅，胡萝卜售价为1.09美元/磅。在添加运费之前，100美元的订单有5%的打折优惠。少于或等于5磅的订单收取6.5美元的运费和包装费，5磅-20磅的订单收取14美元的运费和包装费，超过20磅的订单在14美元吗的基础上每续1磅增加0.5美元。编写一个程序，在循环中用switch语句实现用户输入不同的字母时有不同的响应，即输入a的响应是让用户输入洋蓟的磅数，b是甜菜的磅数，c是胡萝卜的磅数，q是退出订购。程序要记录累计的重量。即，如果用户输入4磅的甜菜，然后输入5磅的甜菜，程序应该报告9磅的甜菜。然后，该程序要计算货物总价、折扣（涂过油的话）、运费和包装费。随后，程序应显示所有的购买信息：武平售价、订购的重量（单位：磅）、订购的蔬菜费用、订单的总费用、折扣（如果有的哈）、运费和宝篆非、以及所有的费用总额。
#include <stdio.h>
#define BREAK1 5 //磅数第一个判断点
#define BREAK2 20 //磅数第二个判断点
#define Break1 100 //蔬菜价格总额判断点
#define discount 0.05 //折扣
#define charge1 6.5 //一阶运费和包装费
#define charge2 14 //二阶运费和包装费
#define charge3_per 0.5 //三阶运费和包装费（每磅）
#define price1 2.05 //洋蓟单价
#define price2 1.15 //甜菜单价
#define price3 1.09 //胡萝卜单价
int main(void)
{
double pound = 0.0; //用户输入磅数
double pound1 = 0.0; //洋蓟磅数
double pound2 = 0.0; //甜菜磅数
double pound3 = 0.0; //胡萝卜磅数
double totalpound = 0.0; //总磅数
char choice; //用户选择的字母
double Discount = 0.0; //折扣
double veg_fee = 0.0; //蔬菜总价
double trans_fee = 0.0; //运费和包装费
printf("Enter the number corresponding to the vegetable you want to purchase:\n");
printf("a) 洋蓟 b) 甜菜\n");
printf("c) 胡萝卜 q) quit\n");
while((choice = getchar()) != 'q') //q退出订购
{
if(choice < 'a' || choice > 'c') //判断有效输入
{
printf("Enter the right letter\n");
getchar();
continue;
}
printf("Enter how much do you want to purchase(pounds):");
scanf("%lf", £);
totalpound += pound; //加总磅数
switch (choice){ //加各个菜的磅数
case 'a': veg_fee += pound * price1;
pound1 += pound;
break;
case 'b': veg_fee += pound * price2;
pound2 += pound;
break;
case 'c': veg_fee += pound * price3;
pound3 += pound;
break;
}
printf("Enter the number corresponding to the vegetable you want to purchase:\n");
printf("a) 洋蓟 b) 甜菜\n");
printf("c) 胡萝卜 q) quit\n");
getchar();
}
if(totalpound <= BREAK1) //判断运费和包装费
trans_fee = charge1;
else if(totalpound > BREAK1 && totalpound <= BREAK2)
trans_fee = charge2;
else
trans_fee = charge2 + (totalpound - BREAK2) * charge3_per;
if(veg_fee >= Break1) //判断折扣情况
{
Discount = discount * veg_fee;
}
printf("your purchase information is as the following:\n");
printf("洋蓟: %.2lf pound(s), $%.2lf/pound\n", pound1, price1);
printf("甜菜: %.2lf pound(s), $%.2lf/pound\n", pound2, price2);
printf("胡萝卜: %.2lf pound(s), $%.2lf/pound\n", pound3, price3);
printf("your vegetable fee is $%.2lf, transport and wrapper fee is $%.2lf, fee before discount(if you have) is $%.2lf\n", veg_fee, trans_fee, veg_fee + trans_fee);
if(Discount > 0)
printf("your discount is $%.2lf for your purchase is above $100\n", Discount);
printf("you should pay $%.2lf in the end", veg_fee + trans_fee - Discount);
return 0;
} 
