C primer plus第七章习题

最新推荐文章于 2024-08-25 19:16:29 发布

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这篇博客回顾了C Primer Plus第七章的编程练习，作者分享了在忙碌工作中仍保持编程热情的经历，并对部分练习题进行了简单解答，包括使用无限循环、getchar函数的误用、putchar的注意点，以及编写get_int和isprime函数的过程。

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复习题很轻松的通过了，不赘述了。
最近工作开始忙了，第七章看的效果很慢，但是兴趣还在上了24小时的班之后居然能兴致勃勃的写代码，当做休息吧。
瞎扯结束，以上。

编程练习

1.

/很简单，看会书上例题就可以。/
#include

2.

#include <stdio.h>
int main(void)
{
    char ch;
    int n;

    for( n = 1;ch = getchar() != '#';n++)
    {
        printf("%c %d", ch, ch);
        if(n%8==0)
            printf("\n");
    }
    return 0;
}

3.

#include <stdio.h>
int main(void)
{
    int a = 0, b = 0, c = 0, d = 0, i;

    printf("Please enter the number:\n");
    while(1)
    {
        scanf("%d", & i);
        if(i == 0)
            break;
        if(i%2==0)
            {
                a++;
                b += i;
            }
        else 
            {
                c++;
                d += i;
            }
    }
    printf("%d %d %d %d", a, b/a, c, d/c);
    return 0;
}

变量名依然取不好。while（1）可以无限循环，直到输入0，break这个循环。做错的原因是用了getchar…….用顺手了………

4.

#include <stdio.h>
int main(void)
{
    char ch;
    int a,b;

    while((ch = getchar()) != '#')
    {
        if(ch == '.')
        {
            putchar('!');
            a++;
        }
        else if(ch == '!')
        {
            putchar('!');
            b++;
        }
        else
            putchar(ch);
    }
    printf("%d times . to !", a);
    printf("%d times ! to !!", b);
    return 0;
}

putchar（”）需要注意。

5.

#include <stdio.h>
int main(void)
{
    int num, odd = 0, even = 0, sum_odd = 0, sum_even = 0;

    printf("Plese enter the number:\n");
    while(1)
    {
        scanf("%d", &num);
        if(num == 0)
            break;
        switch(num % 2 != 0)
        {
        case 1: sum_odd += num;
                odd++;
                break;
        case 0: sum_even += num;
                even++;
        }
    }
    printf("odd count is %d.\n", sum_odd);
    printf("odd average is %d.\n", sum_odd / odd);
    printf("even count is %d.\n", sum_even);
    printf("even count is %d.\n", sum_even / even);
    return 0;
}

6.

#include <stdio.h>
int main(void)
{
    int count = 0;
    char first = 0,second ;

    while((second = getchar()) != '#')
    {
        if((first == 'e') && (second == 'i'))
            count++;
            first = second;
    }
    printf("'ei' appeared %d times.\n", count);
    return 0;
}

7.

#include <stdio.h>
#define HOURPER 100
#define TAX1 0.15
#define TAX2 0.2
#define TAX3 0.25

int main(void)
{ 
    float pay, hours, tax;

    printf("Please enter the hours:\n");
    scanf("%f", &hours);
    if(hours > 40.0 )
    {
        hours = 40 + (hours - 40) *1.5;
        pay = hours * HOURPER;
        printf("Pay is %f.\n", pay);
    }
    else
            pay = hours * HOURPER;
    if(pay <= 300)
        tax = pay * TAX1;
    else if(pay <= 450)
        tax = 300 * TAX1 + (pay - 300) * TAX2;
    else
        tax = 300 * TAX1 + 150 * TAX2 + (pay - 450) * TAX3; 
    printf("pay is %f,tax is %f, income is %f\n", pay, tax, pay - tax);
    return 0;
}

8.

#include <stdio.h>
#define TAX1 0.15
#define TAX2 0.2
#define TAX3 0.25

int main(void)
{ 
    float pay, hours, tax, HOURPER;

    while(1)
    {
        printf("Enter the number corresponding to the desired pay rate or action:\n");
        printf("1) $8.75/hr\t\t\t2) $9.33/hr\n");
        printf("3) $10.00/hr\t\t\t4) $11.20/hr\n");
        printf("5) quit\n");
        switch(get_int())
        {
            case 1: HOURPER = 8.75;
                    break;
            case 2: HOURPER = 9.33;
                    break;
            case 3: HOURPER = 10.00;
                    break;
            case 4: HOURPER = 11.20;
                    break;
            case 5: printf("quit.\n");
                    return 0;
        }
        printf("Pleas enter the hours:\n");
        scanf("%f", &hours);
        if(hours > 40.0 )
        {
            hours = 40 + (hours - 40) *1.5;
            pay = hours * HOURPER;
            printf("Pay is %f.\n", pay);
        }
        else
                pay = hours * HOURPER;
        if(pay <= 300)
            tax = pay * TAX1;
        else if(pay <= 450)
            tax = 300 * TAX1 + (pay - 300) * TAX2;
        else
            tax = 300 * TAX1 + 150 * TAX2 + (pay - 450) * TAX3; 
        printf("pay is %f,tax is %f, income is %f\n", pay, tax, pay - tax);
        return 0;
    }
}

int get_int(void)
{
    int num;
    char str[40];

    while(scanf("%d", &num) != 1)
    {
        gets(str);
        printf("Please enter the NUMBER!\n");
    }
    while(getchar() != '\n');
    return num;
}

定义了一个get_int函数，用来过滤非法选择的数字，得到1到5的选择整数。

9.

#include <stdio.h>
int isprimer(int);

int main(void)
{
    int num,i;
    printf("please enter a positive number:\n");
    scanf("%d", &num);
    for(i=2;i<=num;i++)
        if(isprimer(i))
            printf("%d\t", i);
    printf("\n");
    return 0;
}

int isprimer(int n)
{
    int div;

    for(div =2; div * div <=n; div++)
        if(n % div == 0)
            return 0;
    return 1;
}

isprimer（）是判断素数的函数（记不住就多看，多记几遍），素数返回1，非素数返回0。