C Primer Plus_第8章_字符输入输出和输入确认_编程练习

1.题略

#include <stdio.h>

int main(void)
{
    int ch,i=0;
    printf("Please enter text here(end with Ctrl + Z):\n");
    while (ch=getchar() != EOF)
        i++;
    printf("There are %d characters in text.\n", i);
    return 0;
}

运行结果

输入第一个Ctrl+Z时，并没有结束，下一行再输入Ctrl+Z才检测到EOF。说明我的控制台环境下，文件结尾形式是一行的开始位置Ctrl+Z，而不是任意位置的Ctrl+Z。

 

2.题略

/*  */
#include <stdio.h>
int main(void)
{
    int i=0, ch;
    
    while ((ch = getchar()) != EOF)
    {
        if (ch == '\n')
            printf("\\n%3d  \n",ch);    //换行符就是一个字符，同时它提示读入行缓冲区中的数据
        else if (ch == '\t')
            printf("\\t%3d  ",ch);
        else if ((ch < ' ') && (ch != '\n') && (ch != '\t'))
            printf("^%c%3d  ",ch+64,ch);
        else
            printf("%-2c%3d  ",ch,ch);
        i++;
        if(i%10 == 0)
            putchar('\n');
    }
}

 

3.题略

/*统计大小字母个数*/
#include <stdio.h>
#include <ctype.h>　　//关联函数isupper(),islower()

int main(void)
{
    int count_up = 0, count_low = 0;
    int count_other = 0;
    int ch;

    printf("Please enter some text: \n");
    while ((ch = getchar()) != EOF)
    {
        if (isupper(ch))　　　　//isupper(ch)函数：ch是大写字母的话，函数返回真值1
            count_up++;
        else if (islower(ch))　//islower(ch)函数：ch是小写字母的话，函数返回真值1
            count_low++;
        else
            count_other++;
    }
    printf("There are %d upper letters\n", count_up);
    printf("and %d lower letters\n", count_low);
    printf("and %d other letters\n", count_other);
    return 0;
}

运行结果

 

4.题略

/*报告单词中的字母数*/
#include <stdio.h>
#include <ctype.h>

int main(void)
{
    int CountLet = 0, CountWrd =0;
    int ch, ch_pre=' ';

    printf("Please enter some text (ctrl+z to quit): \n");
    while ((ch = getchar()) != EOF)
    {
        if (isalpha(ch))
            CountLet++;
        if ((isspace(ch) || ispunct(ch)) && isalnum(ch_pre))
            CountWrd++;
        ch_pre = ch;
    }
    printf("There are %d letters and %d words.\n", CountLet, CountWrd);
    printf("There are %d letters in a word on average.\n", CountLet / CountWrd);

    return 0;
}

运行结果

 

5.题略

/*问大小后再猜数*/
#include <stdio.h>
int main(void)
{
    int min,max,mid,ch;

    printf("请输入被猜整数的范围：min（较小的数）和max（较大的数）\n");
    scanf("%d%d",&min,&max);
    printf("min = %d, max = %d\n",min, max);
    mid = min + (max-min)/2;
    printf("is it %d? (please enter y(yes), b(big), s(small))", mid);
    while((ch = getchar ()) != 'y')
    {
        if (ch == 'b')
        {
            max = mid;
            mid = min + (max-min)/2;
            printf("is it %d? (please enter y(yes), b(big), s(small))", mid);
        }
        else if (ch == 's')
        {
            min = mid;
            mid = min + (max-min)/2;
            printf("is it %d? (please enter y(yes), b(big), s(small))", mid);
        }
        else
        {
            if (ch == '\n')
                continue;
            else
                printf("Please just enter y, b, s.\n");
        }
    }
    printf("the number is %d!\n",mid);

    return 0; 
}

自己写的有点复杂了可能，不过运行起来还是可行的

 

6.题略

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

char get_first();

int main(void)
{
    printf("get_first() is %c", get_first());
}

char get_first()
{
    int ch;
    printf("Please enter some words:\n");
    while ((ch = getchar()) && (isspace(ch) == 0))
        continue;
    ch = getchar();
    return ch;
}

8.题略

/**/
#include<stdio.h>
#include<ctype.h>
float get_float(void);
char get_first(void);


int main(void)
{
    char select;
    float num1,num2;
    while(1)
    {
        printf("Enter the operation of your choice:\n");
        printf("a.add            s.subtract:\n");
        printf("m.multiply       d.divide\n");
        printf("q.quit\n");
        select = get_first();
        if( select != 'a' && select != 's' && select != 'm' && select != 'd')
        {
            printf("Bye.\n");
            break;
        }
        printf("Enter first number:");
        num1 = get_float();
        printf("Enter second number:");
        num2 = get_float();
        while( select == 'd' && num2 == 0) 
        {
            printf("Enter a number other than 0:");
            num2 = get_float();
        }
        switch(select)
        {
            case 'a': printf("%.2f + %.2f = %.2f\n",num1, num2, num1 + num2); break;
            case 's': printf("%.2f - %.2f = %.2f\n",num1, num2, num1 - num2); break;
            case 'm': printf("%.2f * %.2f = %.2f\n",num1, num2, num1 * num2); break;
            case 'd': printf("%.2f / %.2f = %.2f\n",num1, num2, num1 / num2); break;
            default : break;
        }
    }
    return(0);
}

float get_float(void) //得到一个合适的浮点数，滤除非法数
{
    float num;
    char str[40];
    while(scanf("%f",&num)!=1)
    {
        gets(str);
        printf("%s is not a number.\n",str);
        printf("Please enter a numbe, such as 2.5, -1.78E8, or 3:");
    }
    while ( getchar() != '\n');
    return num;
}

char get_first(void) //得到字符串中的第一个字符，滤除其他字符
{
    int ch;
    while( isspace( ch = getchar() ) );
    while ( getchar() != '\n');
    return ch;
}