复习题.md

第七章 分支和跳转控制语句 复习题

1. 判断下列表达式时true还是false。

a. 100 > 3 && 'a' > 'c'; // false
b. 100 > 3 || 'a' > 'c'; // true
c. !(100>3); // false

2. 根据下列描述的条件，分别构造一个表达式

a. number等于或大于90，但是小于100 // number>=90 && number < 100;
b. ch不是字符q或k // ch !== 'q' || ch !== 'k';
c. number在1～9之间（包括1和9），但不是5 // number >=1 && number <=9 && number!==5;
d. number不在1～9 // number < 1 && number > 9;

3. 下面的程序关系表达式过于复杂，而且还有些错误，请简化并改正。

#include <stdio.h> 
int main(void)
{
    int weight, height; /* weight以磅为单位，height以英寸为单位 */

    scanf("%d, weight, height);
    if(weight < 100 && height > 64)
        if(height >= 72)
            printf("You are very tall for your weight.\n");
        else if(height < 72 && > 64)
            printf("You are tall for your weight.\n");
    else if(weight > 300 && !(weight <= 300)
                && height < 48)
        if(!(height >= 48))
            printf(" You are quite short for your weight.\n");
    else
        printf("Your weight is ideal.\n");

   return 0;
}

修改版本如下：

#include <stdio.h>
int main(void)
{	
	int weight, height;
	
	scanf("%d %d", &weight, &height);  
	if (weight < 100 && height > 64)
		if (height >= 72)
			printf("You are very tall for your weight. \n");
		else 		
			printf("You are tall for your weight. \n");
	else if (weight > 300 && height < 48)	
		printf(" Your are quite short for your weight. \n"); 
		else
			printf("Your weight is ideal. \n");

	return 0;
}

4. 下列各个表达式的值是多少？

a. 5>2 // true,即是1
b. 3+4 > 2 && 3<2 // false，即是0
c. x>=y || y > x // 1
d. d = 5 + (6 > 2) // 6 
e. 'X' > 'T' ? 10 : 5 // 10 
f. x > y ? y > x : x > y // 0 

5. 下面的程序将打印什么？

#include <stdio.h>
int main(void)
{
    int num;
    for (num = 1;num <=11;num++)
    {
        if(num %3 == 0)
            putchar('$');
        else 
            putchar('*');
            putchar('#');
        putchar('%');
    }
    putchar('\n');
    return 0;
}
// 打印结果为：*#%*#%$#%*#%*#%$#%*#%*#%$#%*#%*#%

6. 下面的程序将打印什么？

#include <stdio.h>
int main(void)
{
    int i = 0;
    while (i < 3)
    {
        switch (i++){
            case 0:printf("fat ");
            case 1:printf("hat ");
            case 2:printf("cat ");
            default:printf("Oh no!");
        }
        putchar('\n');
    }
    return 0;
}
/*打印结果为： 
fat hat cat Oh no!
hat cat Oh no!
cat Oh no!
*/

7. 下面的程序有哪些错误？

#include <stdio.h>
int main(void)
{
    char ch;
    int lc = 0;
    int uc = 0;
    int oc = 0;
    while ((ch = getchar())!='#')
    {
        if('a' <= ch >= 'z')
            lc++;
        else if (!(ch < 'A') || !(ch) > 'z')
            uc++;
        oc++;
    }
    printf(%d lowercase, %d uppercase, %d other,lc,uc,oc);
    return 0;
}

修改后的程序：

#include <stdio.h>
#include <ctype.h>
int main(void)
{
    char ch;
    int lc = 0;
    int uc = 0;
    int oc = 0;
    while ((ch = getchar())!='#')
    {
        if(islower(ch))
            lc++;
        else if (isupper(ch))
            uc++;
        else
            oc++;
    }
    printf("%d lowercase, %d uppercase, %d other \n",lc,uc,oc);
    return 0;
}

8. 下面的程序将打印什么？

#include <stdio.h>
int main(void)
{
    int age = 20;
    while (age++ <= 65) // 
    {
        if ((age % 20)==0)
            printf("You are %d . Here is a raise.\n",age);
        if (age =65)
            printf("You are %d . Here is your gold watch.\n",age);
    }
    return 0;
}
/*打印结果：死循环打印如下内容
You are %d . Here is your gold watch. 
*/

9. 给定下面的输入时，以下程序将打印什么？

/*
q
c
h
b
*/
#include <stdio.h>
int main(void)
{
    char ch;

    while((ch = getchar()) != '#')
    {
        if(ch == '\n')
            continue;
        printf("Step 1\n");
        if(ch == 'c')
            continue;
        else if(ch == 'b')
            break;
        else if(ch == 'g')
            goto laststep;
        printf("Step 2\n");
        laststep: printf("Step 3\n");
    }
    printf("Done!\n");
    return 0;
}
/*打印结果为：
q
Step 1
Step 2
Step 3
c
Step 1
g
Step 1
Step 3
b
Step 1
Done!
*/

10. 重写复习题9，但这次不能使用continue 和 goto语句。

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

    while((ch = getchar()) != '#')
    {
        if(ch != '\n')
        {
            printf("Step 1\n");
            if(ch != 'c')
            {
                if(ch == 'b')
                    break;
                if(ch != 'g')
                    printf("Step 2\n");
                printf("Step 3\n");
            }
        }
    }
    printf("Done!\n");
    return 0;
}