c primer plus 7编程练习

1、

#include <stdio.h>
#include <ctype.h>

int main(void)
{
    char ch;
    int n_space = 0, n_lines = 0, n_other = 0; 
    
    
    while((ch = getchar()) != '#')
    {
        if(ch == ' ')
            n_space++;
        else if(ch == '
')
            n_lines++;
        else
            n_other++;
    }
    
    printf("n_space: %d;  n_lines: %d;  n_other: %d
", n_space, n_lines, n_other);
    
    return 0;
} 

#include <stdio.h>
int main(void)
{
    char ch;
    int blank = 0;
    int endline = 0;
    int others = 0;
    
    printf("please input chars(# to quit): ");
    
    while((ch = getchar()) != '#')
    {
        if(ch == ' ')
            blank++;
        else if(ch == '
')
            endline++;
        else
            others++;
    }
    
    printf("blank: %d;  endline: %d;  other: %d.
", blank, endline, others);
    
    return 0;
}

2、

#include <stdio.h>

int main(void)
{
    char ch;
    int n = 1;
    
    while((ch = getchar()) != '#')
    {
        printf("%c→%d  ", ch, ch);
        if(n++ % 8 == 0)
            printf("
");
    }
    
    return 0;
}

#include <stdio.h>

int main(void)
{
    char ch;
    int counter = 0;
    printf("please input chars(# for exit): ");
    
    while((ch = getchar()) != '#')
    {
        if(counter++ % 8 == 0)
            printf("
");
        if(ch == '
')
            printf("\n-%03d  ", ch);
        else if(ch == '	')
            printf("\t-%03d  ", ch);
        else
            printf("%c-%03d  ", ch, ch);
    }
    
    return 0;
}

3、

#include <stdio.h>

int main(void)
{
    int num;
    int n_even = 0;
    int sum_even = 0;
    int odd;
    int n_odd = 0;
    int sum_odd = 0;
    

    do
    {
        printf("please input the num(0 to quit): ");
        scanf("%d", &num);
        if(num % 2 == 0 && num != 0)
        {
            n_even++;
            sum_even += num;
        }
        if(num % 2 == 1)
        {
            n_odd++;
            sum_odd += num;
        }
    }
    while(num != 0);
    
    if(n_even > 0)
    {
        printf("n_even: %d.
", n_even);
        printf("average_even: %.2f.
", (double)sum_even / n_even);
    }
    else
        printf("no even num!
");
    
    printf("
");
    
    if(n_odd > 0)
    {
        printf("n_odd: %d.
", n_odd);
        printf("average_odd: %.2f.
", (double)sum_odd / n_odd);
    }
    else
        printf("no odd num!");
    
    return 0;
}

#include <stdio.h>

int main(void)
{
    int num;
    int n_even = 0;
    int sum_even = 0;
    int n_odd = 0;
    int sum_odd = 0;
    
    printf("please input the num(0 to quit): ");
    
    while(scanf("%d", &num) == 1)
    {
        if(num == 0)
            break;
        if(num % 2 == 0)
        {
            n_even++;
            sum_even += num;
        }
        else
        {
            n_odd++;
            sum_odd += num;
        }
        printf("please input the num(0 to quit): ");
    }
    
    putchar('
');
    
    if(n_even > 0)
    {
        printf("n_even: %d;  average_even: %.2f.
", n_even, (double)sum_even / n_even);
    }
    else
        printf("no even num inputed!.
");
    
    if(n_odd > 0)
    {
        printf("n_odd: %d;  average_odd: %.2f.
", n_odd, (double)sum_odd / n_odd);
    }
    else
        printf("no odd num inputed.
");
        
    return 0;
}

4、

#include <stdio.h>
int main(void)
{
    int counter = 0;
    char ch;
    printf("please input chars(# for exit): ");
    
    while((ch = getchar()) != '#')
    {
        if(ch == '!')
        {
            printf("!!");
            counter++;
        }
        else if(ch == '.')
        {
            printf("!");
            counter++;
        }
        else
        {
            printf("%c", ch);
        }
    }
    printf("
total times: %d.
", counter);
    
    return 0;
}

#include <stdio.h>

int main(void)
{
    char ch;
    int counter = 0;
    printf("please input chars(# for exit): ");
    
    while((ch = getchar()) != '#')
    {
        if(ch == '!')
        {
            printf("!!");
            counter++;
        }
        else if(ch == '.')
        {
            printf("!");
            counter++;
        }
        else
        {
            printf("%c", ch);
        }
    }
    printf("
replace times: %d.
", counter);
    
    return 0;
}

 5、

#include <stdio.h>

int main(void)
{
    char ch;
    int counter = 0;
    
    printf("please input chars(# for exit): ");
    
    while((ch = getchar()) != '#')
    {
        switch(ch)
        {
            case '!': printf("!!"); counter++; break;
            case '.': printf("!");  counter++; break;
            default: printf("%c", ch); break;
        }
    }
    printf("
replace times: %d.
", counter);
    
    return 0;
}

6、

#include <stdio.h>

int main(void)
{
    char ch;
    char pre;
    int ei_count = 0;
    
    printf("please input the charaters(# to quit): ");
    
    while((ch = getchar()) != '#')
    {
        if(pre == 'e' && ch == 'i')
        {
            ei_count++;
        }
        
        pre = ch;
    }
    
    printf("ei_count: %d.
", ei_count);
    
    return 0;
}

#include <stdio.h>
#include <stdbool.h>

int main(void)
{
    char ch;
    int ei_count = 0;
    bool mark1;
    
    while((ch = getchar()) != '#')
    {
        if(ch == 'e')
            mark1 = true;
        if(ch != 'e' && ch != 'i')
            mark1 = false;
            
        if(mark1 && ch == 'i')
        {
            ei_count++;
        }
        
    }
    
    printf("ei_count: %d.
", ei_count);
    
    return 0;
}

#include <stdio.h>

int main(void)
{
    int counter = 0;
    int halfpair = 0;
    
    char ch;
    printf("please input chars(# for exit): ");
    
    while((ch = getchar()) != '#')
    {
        switch(ch)
        {
            case 'e': halfpair = 1; break;
            case 'i': 
            if(halfpair == 1)
            {
                counter++;
                halfpair = 0;
            };
            break;
            default: halfpair = 0;
        }
    }
    printf("
n_ei: %d
", counter);
    
    return 0;
}

7、

#include <stdio.h>

int main(void)
{
    double sum, tax, pure_in;
    float hour;
    
    
    printf("please input the hours this week(q to quit): ");
    while(scanf("%f", &hour))
    {
        if(hour <= 40)
        {
            sum = hour * 10.00;
        }
        else
        {
            sum = 40 * 10.00 + (hour - 40) * 1.5;
        }
        
        if(sum <= 300)
        {
            tax = sum * 0.15;
        }
        else if(sum > 300 && sum <= 450)
        {
            tax = 300 * 0.15 + (sum - 300) * 0.2;    
        } 
        else
        {
            tax = 300 * 0.15 + 150 * 0.2 + (sum - 450) * 0.25;
        }
        pure_in = sum - tax;
        
        printf("sum: %.2f.
", sum);
        printf("tax: %.2f.
", tax);
        printf("pure_in: %.2f.
", pure_in);
        
        printf("
please input the hours this week(q to quit): ");
    }
    return 0;
}

#include <stdio.h>
#define BASE_SALARY 10
#define EXTRA_SALARY 1.5
#define BASE_TAX 0.15
#define EXTRA_TAX 0.2
#define EXCEED_TAX 0.25

int main(void)
{
    float salary, tax, taxed_salary;
    float hours;
    
    printf("please enter the working hours of this week(q to quit): ");
    
    while(scanf("%f", &hours))
    {
        if(hours < 40)
        {
            salary = hours * BASE_SALARY;
        }
        else
        {
            hours = 40 + (hours - 40) * EXTRA_SALARY;
            salary = hours * BASE_SALARY;
        }
        
        if(salary <= 300)
        {
            tax = salary * BASE_TAX;
        }
        else if(salary > 300 && salary <= 450)
        {
            tax = 300 * BASE_TAX + (salary - 300) * EXTRA_TAX;
        }
        else
        {
            tax = 300 * BASE_TAX + 150 * EXTRA_TAX + (salary - 450) * EXCEED_TAX;
        }
        
        taxed_salary = salary - tax;
        printf("salary: %.2f.
", salary);
        printf("tax   : %.2f.
", tax);
        printf("taxed_salary: %.2f.
", taxed_salary);
        
        printf("please enter the working hours of this week(q to quit): ");
    }    
    return 0;
}

8、

#include <stdio.h>
#define EXTRA_SALARY 1.5
#define BASE_TAX 0.15
#define EXTRA_TAX 0.2
#define EXCEED_TAX 0.25

int main(void)
{
    float salary, tax, taxed_salary;
    float hours;
    int tab;
    float BASE_SALARY;
    
    
    printf("Enter the number corresponding to the desired pay rate of action: 
");
    printf("1) $8.75/hr           2) $9.33/hr
3) $10.00/hr          4) $11.20/hr
5) quit");
    printf("

your choice(1-5): ");
    while(scanf("%d", &tab))
    {
        if(tab == 5)
            break;
        else if(tab != 1 && tab != 2 && tab != 3 && tab != 4)
            {
                printf("input error, the range is (1-5): ");
                continue;
            }
        else
        {
            switch(tab)
            {
                case 1: BASE_SALARY = 8.75; break;
                case 2: BASE_SALARY = 9.33; break;
                case 3: BASE_SALARY = 10.00; break;
                case 4: BASE_SALARY = 11.20; break;
            }
        }
        
        printf("please input the working hours of this week: ");
        scanf("%f", &hours);
        
        if(hours < 40)
        {
            salary = hours * BASE_SALARY;
        }
        else
        {
            hours = hours + (hours - 40) * 1.5;
            salary = hours * BASE_SALARY;
        }
        
        if(salary <= 300)
        {
            tax = salary * 0.15;
        }
        else if(salary > 300 && salary <= 450)
        {
            tax = 300 * 0.15 + (salary - 300) * 0.2;
        }
        else
        {
            tax = 300 * 0.15 + 150 * 0.2 + (salary - 450) * 0.25;
        }
        taxed_salary = salary - tax;
        printf("salary: %.2f.
", salary);
        printf("tax: %.2f.
", tax);
        printf("taxed_salary: %.2f.


  ", taxed_salary); 
        
        printf("Enter the number corresponding to the desired pay rate of action: 
");
        printf("1) $8.75/hr           2) $9.33/hr
3) $10.00/hr          4) $11.20/hr
5) quit");
        printf("

your choice(1-5): ");
    }
    
    return 0;
    
}

#include <stdio.h>
#define EXTRA_HOUR 1.5
#define BASE_TAX 0.15
#define EXTRA_TAX 0.2
#define EXCEED_TAX 0.25

void show_menu(void);

void calc_salary(float base_salary, float hours);

int main(void)
{
    float hours = 0;
    char selected;
    do
    {
        show_menu();
        scanf("%c", &selected);
        switch(selected)
        {
            case '1': printf("hello, you selected $8.75/hr. enter the work hours: ");
            scanf("%f", &hours);
            calc_salary(8.75, hours);
            break;
            case '2': printf("hello, you selected $9.33/hr. enter the work hours: ");
            scanf("%f", &hours);
            calc_salary(9.33, hours);
            break;
            case '3': printf("hello, you selected $10.00/hr. enter the work hours: ");
            scanf("%f", &hours);
            calc_salary(10.00, hours);
            break;
            case '4': printf("hello, you selected $11.2/hr. enter the work hours: ");
            scanf("%f", &hours);
            calc_salary(11.2, hours);
            break;
            case '5': break;
            default: printf("error selected! please retry!
");
            break;
        }
        while(getchar() != '
')
            continue;
    }
    while(selected != '5');
        
    return 0;
}

void show_menu(void)
{
    printf("Enter the number corresponding to the desired pay rate or action: 
");
    printf("1) $8.75/hr           2) $9.33/hr
");
    printf("3) $10.00/hr          4) $11.20/hr
");
    printf("5) quit
");
    
}


void calc_salary(float base_salary, float hours)
{
    float salary, tax, taxed_salary;
    
    if(hours < 40)
    {
        salary = hours * base_salary;
    }
    else
    {
        hours = hours + (hours - 40) * EXTRA_HOUR;
        salary = hours * base_salary;
    }
    
    if(salary <= 300)
    {
        tax = salary * BASE_TAX;
    }
    else if(salary > 300 && salary <= 450)
    {
        tax = 300 * BASE_TAX + (salary - 300) * EXTRA_TAX;
    }
    else
    {
        tax = 300 * BASE_TAX + 150 * EXTRA_TAX + (salary - 450) * EXCEED_TAX;
    }
    taxed_salary = salary - tax;
    
    printf("salary: %.2f.
", salary);
    printf("tax   : %.2f.
", tax);
    printf("taxed_salary: %.2f.
", taxed_salary);
}

#include <stdio.h>
#define OVER_WORK 1.5
#define BASE_TAX 0.15
#define EXTRA_TAX 0.2
#define EXCEED_TAX 0.25
int get_num(void);
void calculat_salary(float time, float price);

int main(void)
{
    int num;
    float work_time;
    float price;
    
    num = get_num();
    while(num != 5)
    {
        printf("please input your work time a week: ");
        scanf("%f", &work_time);
        switch(num)
        {
            case 1: price = 8.75; calculat_salary( work_time,  price); break;
            case 2: price = 9.33; calculat_salary( work_time,  price); break;
            case 3: price = 10.00; calculat_salary( work_time,  price); break;
            case 4: price = 11.20; calculat_salary( work_time,  price); break;
            default: printf("program error.
"); break;
        }
        putchar('
');
        num = get_num();
    }
}
 
int get_num(void)
{
    int num;
    printf("1) $8.75/hr            2) $9.33/hr
");
    printf("3) $10.00/hr           4) $11.20/hr
");
    printf("5) quit/
");
    printf("please input your choice: ");
    
    while(scanf("%d", &num) != 1 || num < 1 || num > 6)
    {
        printf("
you can only input 1 - 5.
");
        printf("1) $8.75/hr            2) $9.33/hr
");
        printf("3) $10.00/hr           4) $11.20/hr
");
        printf("5) quit/
");
        printf("please input again: ");
        while(getchar() != '
')
            continue;
    }
    
    return num;
}

void calculat_salary(float time, float price)
{
    float salary_sum;
    float tax;
    float salary_taxed;
    
    if(time <= 40)
    {
        salary_sum = time * price;    
    }
    else
    {
        time = 40 + (time - 40) * OVER_WORK;
        salary_sum = time * price;
    }
    
    if(salary_sum <= 300)
    {
        tax = salary_sum * BASE_TAX;
    }
    else if(salary_sum > 300 && salary_sum <= 450)
    {
        tax = 300 * BASE_TAX + (salary_sum - 300) * EXTRA_TAX; 
    }
    else
    {
        tax = 300 * BASE_TAX + 150 * EXTRA_TAX + (salary_sum - 450) * EXCEED_TAX;
    }
    salary_taxed = salary_sum - tax;
    
    printf("salary_sum: %.2f.
", salary_sum);
    printf("tax: %.2f.
", tax);
    printf("salary_taxed: %.2f
", salary_taxed);
}

9、

#include <stdio.h>

int main(void)
{
    int num;
    
    printf("please input an positive num(q to quit): ");
    while(scanf("%d", &num) && num > 0)
    {
        int i, j;
        
        for(i = 2; i < num; i++)
        {    
            int k = 0;
               for(j = 2; j < num; j++)
            {
                if(i % j == 0)
                    k++;                
            }
            if(k <= 1)
                printf("su shu: %d.
", i);
            
        }
        printf("
please input an positive num(q to quit): ");
    }
    
    return 0;
}

#include <stdio.h>

int main(void)
{
    int num;
    
    printf("please input an positive num(q to quit): ");
    while(scanf("%d", &num))
    {
        if(num < 2)
        {
            printf("input error, the range is >= 2, retry: ");
            continue;
        }
        else
        {
            int i, j;
            for(i = 2; i < num; i++)
            {    
                int k = 0;
                   for(j = 1; j * j <= i; j++) // ???
                {
                    if(i % j == 0)
                        k++;                
                }
                if(k == 1 )
                    printf("su shu: %d.
", i);
                
            }
            printf("
please input an positive num(q to quit): ");
        }
    }
    
    return 0;
}

#include <stdio.h>

int main(void)
{
    int datum;
    do   // 出口型循环控制 
    {
        printf("Enter a number(0 to quit): ");
        scanf("%d", &datum);
        if(datum < 2)
        {
            if(datum == 0)
                break;     // datum = 0, 退出循环 
            printf("%d is out of range, retry.
", datum);
            continue;  // 其他小于2的情况，跳出该次迭代, 小于2的数不存在素数（质数） 
        }
        
        printf("you input %d, so the prime from %d to 2 is: ", datum, datum);
        
        int i, j;
        for(i = datum; i > 1; i--)  //外层循环从测定数递减到2 
        {
            int is_prime = 1;  // 首先设定素数的标记， 
            for(j = 2; j <= i / 2; j++)
            {
                if(i % j == 0) // i % j == 0意味着 i除了1和本身外还有其他约数，也就是说i不是素数。 
                {
                    is_prime = 0; // 检测到i为素数时，修改标记 
                    break;    // 此处break终止内层迭代，一旦检测到i有1和本身外的第一个约数，立即终止i的判断 
                }    
            }    
            if(is_prime == 1) // 检测标记是否发生变化，也就是说同过一次迭代，素数标记is_prime没有发生变化，该轮迭代中的i是素数 
            {
                printf("%d ", i);
            }
        } 
        printf("
"); // 将输出的所有素数换行 
    }
    while(datum != 0);
    
    return 0; 
}

#include <stdio.h>

int main(void)
{
    int num;
    
    printf("please input an num(q to quit): ");
    
    while(scanf("%d", &num))
    {
        if(num < 2)
        {
            printf("input error, the range is >= 2, retry: ");
            continue;    
        }    
        
        int i, j;
        for(i = 2; i < num; i++)
        {
            int marker = 0;
            for(j = 2; j <= i / 2; j++) // 2和3明显是素数 ，实际的循环是从 i = 4 开始进行的 
            {
                if(i % j == 0)
                {
                    marker = 1;
                    break;
                }
            }
            if(marker == 0) 
            {
                printf("prime: %d.
", i);
            }
        }
        printf("please input an num(q to quit): ");
    }    
    return 0;
} 

 10、

#include <stdio.h>
#define BASE1 17850
#define BASE2 23900
#define BASE3 29750
#define BASE4 14875
#define TAXRATE1 0.15
#define TAXRATE2 0.28


int main(void)
{
    int category;
    
    printf("please choose category according the following instruction: 
");
    printf("1) bachelor;       2) hoster;
");
    printf("3) marry_share;    4) marry_dovorce
");
    printf("input your choice(q to quit): ");
    
    while(scanf("%d", &category))
    {
        if(category < 1 || category > 4)
        {
            printf("input error, input 1 - 4(q to quit): ");
            continue;    
        }    
        float salary, tax;
        printf("please input you salary: ");
        scanf("%f", &salary);
        
        switch(category)
        {
            case 1: tax = salary > BASE1 ? BASE1 * TAXRATE1 + (salary - BASE1) * TAXRATE2 : salary * TAXRATE1; break;
            case 2: tax = salary > BASE2 ? BASE2 * TAXRATE1 + (salary - BASE2) * TAXRATE2 : salary * TAXRATE1; break;
            case 3: tax = salary > BASE3 ? BASE3 * TAXRATE1 + (salary - BASE3) * TAXRATE2 : salary * TAXRATE1; break;
            case 4: tax = salary > BASE4 ? BASE4 * TAXRATE1 + (salary - BASE4) * TAXRATE2 : salary * TAXRATE1; break;
        }
            
        printf("your tax: %.2f.


", tax);
        
        printf("please choose category according the following instruction: 
");
        printf("1) bachelor;       2) hoster;
");
        printf("3) marry_share;    4) marry_dovorce
");
        printf("input your choice(q to quit): ");
    }    
    return 0;
} 

#include <stdio.h>
#define SINGLE 17850
#define HOLDER 23900
#define MARRY 29750
#define DIVORCE 14875
#define BASE_TAX 0.15
#define EXTRA_TAX 0.28

int main(void)
{
    char type;
    float salary;
    float tax, salary_taxed;
    
    do
    {
        printf("please select tax type. ther are four types: 
");
        printf("1)single        2)holder       3)marry       4)divorced       5)quit:");
        scanf("%c", &type);
        switch(type)
        {
            case '1': 
            printf("enter your salary: ");
            scanf("%f", &salary);
            if(salary <= SINGLE)
            {
                tax = salary * BASE_TAX;
                salary_taxed = salary - tax;
            }
            else
            {
                tax = SINGLE * BASE_TAX + (salary - SINGLE) * EXTRA_TAX;
                salary_taxed = salary - tax;    
            }
            printf("hi, your salary is %.2f, tax is %.2f,  salary_taxed is %.2f.
", salary, tax, salary_taxed);
            break;
            
            case '2':
            printf("enter you salary: ");
            scanf("%f", &salary);
            if(salary <= HOLDER)
            {
                tax = salary * BASE_TAX;
                salary_taxed = salary - tax;
            }
            else
            {
                tax = HOLDER * BASE_TAX + (salary - HOLDER) * EXTRA_TAX;
                salary_taxed = salary - tax;
            }
            printf("hi, your salary is %.2f, tax is %.2f, salary_taxed is %.2f.
", salary, tax, salary_taxed);
            break;
            
            case '3':
            printf("enter your salary: ");
            scanf("%f", &salary);
            if(salary <= MARRY)
            {
                tax = salary * BASE_TAX;
                salary_taxed = salary - tax;
            }
            else
            {
                tax = MARRY * BASE_TAX + (salary - MARRY) * EXTRA_TAX;
                salary_taxed = salary - tax;
            }
            printf("hi, your salary is %.2f, tax is %.2f, salary_taxed is %.2f.
", salary, tax, salary_taxed);
            break;
            
            case '4':
            printf("enter your salary: ");
            scanf("%f", &salary);
            if(salary <= DIVORCE)
            {
                tax = salary * BASE_TAX;
                salary_taxed = salary - tax;
            }
            else
            {
                tax = DIVORCE * BASE_TAX + (salary - DIVORCE) * EXTRA_TAX;
                salary_taxed = salary - tax;
            }
            printf("hi, your salary is %.2f, tax is %.2f, salary_taxed is %.2f.
", salary, tax, salary_taxed);
            break;
            
            case '5':
                break;
            
            default: 
            printf("wrong type, please retry.
");
        }    
        while(getchar() != '
')
            continue;
    }
    while(type != '5');
    
    return 0;    
} 

11、

#include <stdio.h>
#define PRICE_ARTI 2.05
#define PRICE_BEET 1.15
#define PRICE_CARROT 1.09
#define DISCOUNT 0.05

void show_menu(void);

float get_weight(void);

int main(void)
{
    float w_arti = 0;
    float w_beet = 0;
    float w_carrot = 0;
    char selected;
    float weight, amount, rebate, freight, total;
    do
    {
        show_menu();
        scanf("%c", &selected);
        switch(selected)
        {
            case 'a':
                w_arti += get_weight();
                break;
            case 'b':
                w_beet += get_weight();
                break;
            case 'c':
                w_carrot += get_weight();
                break;
            case 'q':
                break;
            default:
                printf("error input, retry!
");
                break;
        }
    while(getchar() != '
')
        continue;
    }while(selected != 'q');
    
    amount = w_arti * PRICE_ARTI + w_beet * PRICE_BEET + w_carrot * PRICE_CARROT;
    weight = w_arti + w_beet + w_carrot; 
    
    if(amount >= 100)
        rebate = amount * DISCOUNT;
    else
        rebate = 0;
    
    if(weight <= 5)
        freight = 6.5;
    else if(weight > 5 && weight <= 20)
        freight = 14;
    else
        freight = 14 + (weight - 20) * 0.5;
    total = amount + freight - rebate;
    
    printf("

The price of vegetable:
artichoke %g$/pound,  beet %g$/pound, carrot %g$/pound.
", PRICE_ARTI, PRICE_BEET, PRICE_CARROT);
    printf("you order %g pound artichoke, %g pound beet,  %g pound carrot.
", w_arti, w_beet, w_carrot);
    printf("you total order %g pounds,  discount %g$,  amount %g$,  freight %g$,  total  %g$.
", weight, rebate, amount, freight, total);
    
    printf("Done
");
    
    return 0;
}

void show_menu(void)
{
    printf("
************************************************************************
");
    printf("Enter the char corresponding to the desired vegetable.
");
    printf("a) artichoke           b) beet
");
    printf("c) carrot              d) quit & checkout
");
    printf("please input the vegetable you want to buy(a, b, c or q for quit): ");
    
}

float get_weight(void)
{
    float weight;
    printf("please input how many pounds you buy: ");
    scanf("%f", &weight);
    printf("ok, add %g pound to cart.
", weight);
    return weight;
}

#include <stdio.h>
#define ARTI_PRICE 2.05
#define BEET_PRICE 1.15
#define CARROT_PRICE 1.09
#define DISCOUNT 0.05


int main(void)
{
    char selected;
    float weight;
    float artisum = 0;
    float beetsum = 0;
    float carrotsum = 0;
    float totalweight;
    float vegeprice;
    float rebate;
    float freight;
    float finalprice;
    
    do
    {
        printf("please choose (a, b or c): 
");
        printf("a) arti       b) beet     c) carrot     q) quit and check:  ");
        scanf("%c", &selected);
        
        switch(selected)
        {
            case 'a':
                while(getchar() != '
')
                    continue;
                printf("input the weight for arti: ");
                scanf("%f", &weight);
                artisum += weight;
                printf("add %.2f pound arti.
", weight);
                break;
            case 'b':
                while(getchar() != '
')
                    continue;
                printf("input the weight for beet: ");
                scanf("%f", &weight);
                beetsum += weight;
                printf("add %.2f pound beet.
", weight);
                break;
            case 'c':
                while(getchar() != '
')
                    continue;
                printf("input the weight for carrot: ");
                scanf("%f", &weight);
                carrotsum += weight;
                printf("add %.2f pound carrot.
", weight);
                break;
            case 'q':
                break;
            default:
                printf("input error, choose a, b, c or q, retry: ");
        }
        while(getchar() != '
')
            continue;
    }
    while(selected != 'q');
    
    if(artisum == 0 && beetsum == 0 && carrotsum == 0 )
    {
        printf("
you choose nothing!
");
    }
    else
    {
        printf("

arti: %.2f$/hr;   beet: %.2f$/hr;    carrot: %.2f$/hr
",ARTI_PRICE,BEET_PRICE,CARROT_PRICE);
        totalweight = artisum + beetsum + carrotsum;
        vegeprice = artisum * ARTI_PRICE + beetsum * BEET_PRICE + carrotsum * CARROT_PRICE;
        
        if(vegeprice >= 100)
        {
            rebate = vegeprice * DISCOUNT;
        }
        else
        {
            rebate = 0;
        }
        
        if(totalweight <= 5)
        {
            freight = 6.5;    
        }
        else if(totalweight > 5 && totalweight <= 20)
        {
            freight = 14;
        }
        else
        {
            freight = 14 + (totalweight - 20) * 0.5;
        }
        
        finalprice = vegeprice + freight - rebate;
        
        if(artisum != 0)
            printf("arti weight:       %10.2f.
", artisum);
        if(beetsum != 0)
            printf("beet weight:        %10.2f.
", beetsum);
        if(carrotsum != 0)
            printf("carrot weitht:   %10.2f.
", carrotsum);
        printf("total weight:    %10.2f.
", totalweight);
        printf("vegetable price: %10.2f.
", vegeprice);
        printf("rebate:          %10.2f.
", rebate);
        printf("freight:         %10.2f.
", freight);
        printf("finalprice:      %10.2f
", finalprice); 
    }
    
    
    
    return 0;
}