记录——《C Primer Plus （第五版）》第七章编程练习第十一题

ABC Mail Order Grocery朝鲜蓟的售价是1.25美元/磅，甜菜的售价是0.65美元/磅，胡萝卜的售价是0.89美元/磅。在添加运输费用之前，他们为100美元的订单提供5%的打折优惠。对5磅或以下的定单收取3.50美元的运输和装卸费用；超过5磅而不足20磅的定单收取1O.OO美元的运输和装卸费用：20磅或以上的运输，在8美元基础上每磅加收0.1美元。编写程序，在循环中使用switch语句，以便对输入的响应是让用户输入所需的a朝鲜蓟磅数，b甜菜的磅数，c胡萝卜的磅数，而q允许用户退出订购过程。然后程序计算总费用、折扣和运输费用（如果有运输费的话），以及总数。随后程序应该显示所有的购买信息：每磅的费用、订购的磅数、该订单每种蔬菜的费用、订单的总费用、折扣，如果有的话加上运输费用，以及所有费用的总数。

# include <stdio.h># define PRICEA 1.25     //a物品的单价# define PRICEB 0.65# define PRICEC 0.89# define COST_POUND_LV1 3.50   //一级运费# define COST_POUND_LV2 10.00# define COST_POUND_LV3 8.00# define COST_POUND_LV3_ADD 0.10# define DISCOUNT 0.05double getweight(double);void clear();int main(void){    char ch;    double pounds[3] = {0};  //物品重量    double cost_total=0;   //  总费用    double cost_transport=0;  //总运输费用    double cost_discount=0;  //折扣    double pound_total = 0;   //总磅数    double order = 0;   //总订单    double cost_a_total=0;  //朝鲜蓟的总价    double cost_b_total=0;    double cost_c_total=0;    printf("请输入要选择的商品的序号：\n");    printf("a 朝鲜蓟, b 甜菜, c 胡萝卜\n");    while(printf("\n请选择您要订购的货品："),(ch=getchar())!='q'){          switch(ch){              case 'a':                  pounds[0]=getweight(pounds[0]);                  break;              case 'b':                 pounds[1]=getweight(pounds[1]);                  break;              case 'c':                pounds[2]=getweight(pounds[2]);                  break;            default:                printf("输入有误，请重新选择货品。\n");                  clear();                  break;          }      }     pound_total = pounds[0] + pounds[1] + pounds[2];      //总磅数    cost_a_total = pounds[0] * PRICEA;    cost_b_total = pounds[1] * PRICEB;    cost_c_total = pounds[2] * PRICEC;    order = cost_a_total + cost_b_total + cost_c_total;//  总订单钱数    if(pound_total >= 20.00)    {        cost_transport = COST_POUND_LV3 + COST_POUND_LV3_ADD * pound_total;    }    else if(pound_total >5)        cost_transport = COST_POUND_LV2;    else if(pound_total >=0)        cost_transport = COST_POUND_LV1;    if(order >= 100.00)    {        cost_discount = order * DISCOUNT;     //  order = order - cost_discount ;    }    cost_total = order + cost_transport - cost_discount;    printf(" 朝鲜蓟每磅%.3lf,订购了%.3lf磅 \n甜菜每磅%.3lf,订购了%.3lf磅 \n胡萝卜每磅%.3lf订购了%.3lf磅\n",PRICEA, pounds[0], PRICEB, pounds[1], PRICEC, pounds[2]);    printf("订购朝鲜蓟花费 %.3lf 订购甜菜花费 %.3lf 订购胡萝卜花费%.3lf\n",cost_a_total, cost_b_total, cost_c_total);    printf("你总共订购花费了%.3lf 打折后费用为%.3lf\n", order, cost_discount);    printf("你花费的运费为%.3lf\n", cost_transport);    printf("你总共花费了%.3lf\n", cost_total);    return 0;}double getweight(double pounds){    double weight;    printf("请输入所需磅数：");    scanf("%lf", &weight);    pounds += weight;    printf("你已购买 %.3lf 磅!\n", pounds);    clear();                      //清空输入的字符    return pounds;}void clear(){    while(getchar() != '\n')        continue;}