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 

# 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 0.05


double 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;
}