C语言程序设计教程课后习题答案

第1章

1-3 CAB

4 .c .obj .exe

5 /* */

6 ;

7 算法

8 ①中级语言：C语言具有高级语言的先进思想又能直接对存储器进行操作，能进行位运算，能实现汇编语言的大部分功能，生成目标代码质量高，程序执行效率高。

②结构化语言：C语言用函数作为程序模块,以实现程序的模块化，语言简洁、紧凑，具有结构化的特点。

③可移植性好：C语言不包含依赖硬件的输入输出机制，使C语言本身不依赖于硬件系统，可移植性好。

9 #include<>

main( ) { ; }

10 #include “”

main()

{

printf(“This is my first C Program!”);

}

第2章

1．yes

2．-3

3．2,1

4．1)a!=b||a<=c 2)x>=4||x<=-4

5．x>20&&x<30||x<-100

6．#include <>

main()

{

int x;

printf(“please input an integar:”);

scanf("%d",&x);

if(x%5==0&&x%7==0) printf("yes\n");

else printf("no\n");

}

7.

#include <>

main()

{

int year,month;

printf("please input the year and month:");

scanf("%d%d",&year,&month);

switch(month)

{

case 1:

case 3:

case 5:

case 7:

case 8:

case 10:

case 12:printf("this month have 31 days.");

break;

case 4:

case 6:

case 9:

case 11:printf("this month have 30 days.");

break;

case 2:if(year%4==0&&year%100!=0||year%400==0)

{

printf("this month have 29 days.");

break;

}

else

{

printf("this month have 28 days.");

break;

}

}

}

8.

#include <>

main()

{

float money;

int year;

printf("\nplease input the money and the year:");

scanf("%f%d",&money,&year);

if(year==1) money+=money**12*year;

if(year==2) money+=money**12*year;

if(year==3||year==4) money+=money**12*year;

if(year>=5&&year<=7) money+=money**12*year;

if(year>=8) money+=money**12*year;

printf("the money is:%f",money);

}

第3章

1

#include ""

main()

{ float x[10],sum=0;

int i=0;

printf("please input 10 numbers(-10e6

while(i<10)

{ scanf("%f",&x[i]);

sum=sum+1/x[i];

i=i+1;

}

printf("the sum of 10 numbers is %.2f\n",sum);

}

2

#include ""

main()

{ int x[100],sum=0,aver,i=0;

printf("please input numbers until 0\n");

scanf("%d",&x[i]);

while(x[i]!=0)

{ sum=sum+x[i];

i=i+1;

scanf("%d",&x[i]);

}

printf("the sum is %d\n",sum);

printf("the average is %.2f\n",float(sum)/i);

}

3

#include ""

#include ""

main()

{ int i=1,j,f;

long int s=0;

while(i<=10)

{ for(f=1,j=1;j<=i;j++)

f=f*j;

s=s+pow(-1,i-1)*f;

i=i+1;

}

printf("s= %ld\n",s);

}

4

#include ""

#include ""

main()

{ int i=0;

float s=;

while(2*i+1<=101)

{ s=s+pow(-1,i)/float(2*i+1);

i=i+1;

}

printf("s= %f\n",s);

}

5

#include ""

#include""

main()

{ int i,j,k,n=0;

for(i=1;i<=9;i++)

for(j=0;j<=9;j++)

for(k=0;k<=9;k++)

if(i*100+j*10+k==i*i*i+j*j*j+k*k*k)

printf("the %d:%d\n",++n,i*100+j*10+k);

printf("the all is %d.\n",n--);

}

6

#include ""

main()

{ int n,i,j;

printf("please input n:");

scanf("%d",&n);

for(i=0;i

{ for(j=0;j

printf("*");

printf("\n");

}

}

7

#include ""

main()

{ char a[81];

int i,j=0,k=0,m=0;

printf("please input a $(length<=80)\n");

for(i=0;(a[i]=getchar())!='\n';i++)

{ if(a[i]>=65&&a[i]<=90)

j++;

else if(a[i]==32)

k++;

else m++;

}

printf("the upper letter is %d\n",j);

printf("the blank is %d\n",k);

printf("the other is %d\n",m);

}

8

#include ""

main()

{ int i,j,k,m=0;

for(i=0;i<=20;i++)

{ for(j=0;j<=50;j++)

for(k=0;k<=100;k++)

if(i*5+j*2+k==100)

printf("the %d wag is 1:%d,2:%d,5:%d\n",++m,k,j,i);

}

printf("the wags is %d\n",m--);

}

9

#include ""

main()

{ int i,j,k,m=0;

for(i=0;i<=3;i++)

{ for(j=0;j<=3;j++)

for(k=0;k<=6;k++)

if(i+j+k==8)

printf("the %d wag is white:%d,red:%d,black:%d\n",++m,i,j,k);

}

printf("the wags is %d\n",m--);

}

10

#include ""

main()

{ long int n;

int i,j,k;

printf("please inpur n:");

scanf("%ld",&n);

if(n%2==1||n<=1)

{ printf("the input is error.\n");

return(1);

}

for(i=2;i<=n/2;i++)

{ for(j=2;j

if(i/j*j==i)

break;

if(j==i)

{for(k=2;k

if((n-i)/k*k==(n-i))

break;

if(k==n-i)

printf("%ld=%d+%d\n",n,i,n-i);

}

}

}

11

#include ""

main()

{int i,j,k,m;

for(i=1;i<=9;i++)

for(j=0;j<=9;j++)

for(k=0;k<=9;k++)

for(m=0;m<=9;m++)

if((i*1000+j*100+k*10+m)*9==(i+j*10+k*100+m*1000))

printf("the number is:%d\n",i*1000+j*100+k*10+m);

}

第4章

1-5 ABDCB 6-10 BCBCA 11-13 ABA

14

#include ""

main()

{

float a1,b1,a2,b2,re1,im1,re2,im2,re3,im3;

printf("Please input the first number:");

scanf("%f %f",&a1,&b1);

printf("Please input the second number:");

scanf("%f %f",&a2,&b2);

re1=a1+a2;

im1=b1+b2;

printf("(%f+j%f)+(%f+j%f)=%f+j%f\n",a1,b1,a2,b2,re1,im1);

re2=a1-a2;

im2=b1-b2;

printf("(%f+j%f)-(%f+j%f)=%f+j%f\n",a1,b1,a2,b2,re2,im2);

re3=a1*a2-b1*b2;

im3=a1*b2+a2*b1;

printf("(%f+j%f)*(%f+j%f)=%f+j%f\n",a1,b1,a2,b2,re3,im3);

}

第5章

1-5 CACCD 6-7 DA

8

#include ""

main()

{

char str[100];

int num1=0,num2=0,i=0;

scanf("%s",str);

while(str[i]!='\0')

{

if(str[i]>='A'&&str[i]<='Z'||str[i]>='a'&&str[i]<='z')

num1++;

else if(str[i]>='0'&&str[i]<='9')

num2++;

i++;

}

printf("num1=%d,num2=%d",num1,num2);

}

9笔者在程序中直接给数组元素赋了值，读者可以修改为用scanf函数读入数值；另外，还可以用第7章宏定义的方法设定数组的长度，从而实现对元素个数不同的数组进行排序。#include ""

main()

{

int a[5]={2,4,1,3,0},i,j,temp;

for(i=0;i<=4;i++)

printf("%d,",a[i]);

printf("\n");

for(j=1;j<=4;j++)

for(i=j;i<=4;i++)

if(a[i]

{

temp=a[j-1];

a[j-1]=a[i];

a[i]=temp;

}

for(i=0;i<=4;i++)

printf("%d,",a[i]);

}

第6章

1-5 AADBA 6 C

7 0 2 4 6 8 10 12 14 16 18

0 2 4 6 8 10 12 14 16 18

8 a+b=9

9 5+4+1=10

10+4+2=16

20+4+3=27

10

加密：

#include ""

main()

{

char string[100],i=0,number=0;

scanf("%s",string);

while(string[i++]!='\0')

number++;

fun1(string,number);

printf("%s",string);

}

fun1(char str[],int num)

{

int i;

for(i=0;i<=num;i++)

if(str[i]>='A'&&str[i]<='V'||str[i]>='a'&&str[i]<='v'||str[i]>='0'&&str[i]<='5') str[i]+=4;

else if(str[i]>'V'&&str[i]<='Z')

str[i]-=22;

else if(str[i]>'v'&&str[i]<='z')

str[i]-=22;

else if(str[i]>'5'&&str[i]<='9')

str[i]-=6;

}

解密

#include ""

main()

{

char string[100],i=0,number=0;

scanf("%s",string);

while(string[i++]!='\0')

number++;

fun2(string,number);

printf("%s",string);

}

fun2(char str[],int num)

{

int i;

for(i=0;i<=num;i++)

if(str[i]>='E'&&str[i]<='Z'||str[i]>='e'&&str[i]<='z'||str[i]>='4'&&str[i]<='9')

str[i]-=4;

else if(str[i]>='A'&&str[i]<'E')

str[i]+=22;

else if(str[i]>='a'&&str[i]<'e')

str[i]+=22;

else if(str[i]>='0'&&str[i]<'4')

str[i]+=6;

}

第8章

一、下列语句是否合法

语句：int *p = &x, x = 13;

点评：不合法，因为x变量没有定义。在执行int *p = &x 时，x变量的定义在后面。

参考：int x = 13, *p = &x;

语句：int *p = &x = 13;

点评：不合法，因为x变量没有定义。在执行int *p = &x = 13 时，x变量没有定义。

参考：int x = 13, *p; p = &x;

语句：int x = 13,*p = x;

点评：不合法，不能把x变量的值赋给指针p。应该把变量x的地址值赋给指针p。

参考：int x = 13, *p; p = &x;

语句：int y[5] = {1,2,3,4,5},*p = y[3];

点评：不合法，不能把数组元素y[3]的值赋给指针p，应该把数组元素y[3]的地址值赋给指针p。

参考：int y[5] = {1,2,3,4,5},*p ; p = &y[3];

语句：int *p = y,y[5] = {1,2,3,4,5};

点评：不合法，因为数组y没有定义。

参考：int y[5] = {1,2,3,4,5},*p; p = y;

语句：int y[5] = {1,2,3,4,5},*p = &y;

点评：不合法，不能把数组y的地址值赋给指针p。数组名y本身是数组y的地址常量值。

参考：int y[5] = {1,2,3,4,5},*p; p = y;或int y[5] = {1,2,3,4,5},*p; p = &y[0];

语句：int *c = &ch,ch = "Hello World";

点评：不合法，ch变量没有定义，字符串"Hello World"不能赋给变量ch。

参考：char *ch = "Hello World!";或char *ch;ch = "Hello World";

语句：char ch[12] = "Hello World",*c = ch;

点评：合法。

思考：char ch[12] = "Hello World！！！",*c = ch;该语句错误，字符个数超出数组ch定义的宽度。

语句：char *c = ch[12] = "Hello World"

点评：不合法，数组ch没有定义。数组ch没有第12个元素。

参考：char *c,ch[12] = "Hello World";c = ch;

语句：char *c,c = 'X',c = &c;

点评：不合法，不能把常量'X'的值赋给指针，不能把指针c的地址值赋给指针c自己。

参考：char *c,ch; ch = 'X',c = &ch;

二、综合练习题参考答案

1．将一字符串复制到另一字符串中。

#include<>

void main()

{ char str1[128],str2[128] = {"Welcome to C Language"};

char *cp1,*cp2;

cp1 = str1;

cp2 = str2;

while(*cp1++ = *cp2++);

puts(str1);

}

2．将一字符串与另一字符串相连接。

#include<>

void main()

{ char str1[128] = {"Welcome "},str2[128] = {"to C Language"};

char *cp1,*cp2;

int i = 0,n = 0;

while(n++,str1[++i] != 0);

cp1 = str1+n;

cp2 = str2;

while(*cp1++ = *cp2++);

puts(str1);

}

3．将字符数组中大写字符改为小写字符，将小写字符改为大写字符。

#include<>

void main()

{ char str1[128] = {"Welcome to C Language"};

char *cp1 = str1;

while(*cp1)

{ if(*cp1 >= 'A' && *cp1 <= 'Z')

*cp1 = *cp1+32;

else if(*cp1 >= 'a' && *cp1 <= 'z')

*cp1 = *cp1-32;

else

*cp1 = *cp1;

cp1++;

}

puts(str1);

}

4．从一字符串中取出部分字符串复制到另一字符串中。#include<>

void main()

{ char ch[128],*cp,str[128],*sp;

int b,n,l=0,i;

cp=ch;

sp=str;

gets(cp);

scanf("%d%d",&b,&n);

while(l++,*(ch+l)!=0);

if(n

{ for(i=0;i

*(sp+i)=*(cp+b+i);

*(sp+i)='\0';

puts(str);

}

else

printf("无数据可以复制");

}

5．完成一整型数组的排序。

#include<>

#include<>

void main()

{ int x[10],i,j,*p,t;

p = x;

for(i = 0;i<10;i++)

x[i] = rand();

for(i = 0;i<9;i++)

for(j = 0;j<9;j++)

if(*(p+j)>*(p+j+1))

{ t = *(p+j);

*(p+j) = *(p+j+1);

*(p+j+1) = t;

}

for(i = 0;i<10;i++)

printf("%d\t",*p++);

}

6．将一个字符串中的字符反序排列。

#include<>

void main()

{ char ch[128],c,*cp1,*cp2;

int i,n = 0;

gets(ch);

cp1 = ch;

cp2 = ch;

while(*cp2!= 0)

{ n++;

cp2++;

}

cp2--;

n = n/2;

for(i = 0;i

{ c = *cp1;

*cp1 = *cp2;

*cp2 = c;

cp1++;

cp2--;

}

puts(ch);

}

7．编函数完成将一字符串中的字符全部改为大写。#include<>

void cove(char *cp)

{ while(*cp!= 0)

{ if(*cp>= 'a' && *cp<= 'z')

*cp = *cp-32;

cp++;

}

}

void main()

{ char ch[128],*cp;

cp = ch;

gets(cp);

cove(cp);

puts(ch);

8．编函数完成从一字符串左边取若干字符复制到另一字符串中。

#include<>

void lm(char *lcp,char *bcp,int n)

{ int i;

for(i = 0;i

*(bcp+i) = *(lcp+i);

*(bcp+i) = '\0';

}

void main()

{ char ch[128],*cp,str[128];

int n,l =0;

gets(ch);

scanf("%d",&n);

while(l++,*(ch+l)!= 0);

if(n

{ cp = ch;

lm(cp,str,n);

puts(str);

}

else

printf("无数据可以复制");

}

第9章

1

#include ""

struct date

{ int year;

int month;

int day;

};

main()

{ struct date re;

int

day[2][12]={{31,29,31,30,31,30,31,31,30,31,30,31},{31,28,31,30,31,30,31,31,30,31,30,31}};

int i,days=0;

printf("input the day(year:month:day):\n");

scanf("%d:%d:%d",&,&,&;

if(%4==0&&%100!=0)||%400==0)

for(i=1;i<;i++)

days+=day[1][i-1];

else

for(i=1;i<;i++)

days+=day[0][i-1];

days+=;

printf("the days is %d\n",days);

}

2

#include ""

main()

{enum weekday{Sun,Mon,Tue,Wed,Thu,Fri,Sat} day; int data;

printf("input the data:");

scanf("%d",&data);

data+=2;

day=(enum weekday)(data%7);

switch(day)

{ case Mon:printf("It is Monday.\n");break;

case Tue:printf("It is Tuesday.\n");break;

case Wed:printf("It is Wednesday.\n");break;

case Thu:printf("It is Thursday.\n");break;

case Fri:printf("It is Friday.\n");break;

case Sat:printf("It is Saturday.\n");break;

case Sun:printf("It is Sunday.\n");break;

default:printf("error\n");

}

}

3

#include ""

struct result

{ int notpass;

int pass;

int good;

};

main()

{ struct result re, *p=&re;

int i,temp;

void output(struct result *);

=0;

=0;

=0;

printf("input 12 integers;\n");

for(i=0;i<12;i++)

{ scanf("%d",&temp);

if(temp<0||temp>100)

{ printf("error!\n");

return(0);

}

else if(temp<60)

++;

else if(temp>=80)

++;

else ++;

}

output(p);

return(1);

}

void output(struct result *p)

{ printf("the result:\n");

printf(" mark: 0-59 60-79 80-100\n");

printf("number: %d %d %d\n",p->notpass,p->pass,p->good); }

4

#include ""

struct stat

{ int length;

int blank;

int letter;

int number;

};

main()

{ struct stat re[2];

char temp;

int k;

void output(struct stat *);

for(k=0;k<2;k++)

{ re[k].length=0;

re[k].blank=0;

re[k].letter=0;

re[k].number=0;

}

for(k=0;k<2;k++)

{ printf("input the %dst $;\n",k+1);

while((temp=getchar())!='\n')

{ re[k].length++;

if(temp==' ')

re[k].blank++;

else if((temp>=65&&temp<=90)||(temp>=97&&temp<=122))

re[k].letter++;

else if(temp>=48&&temp<=57)

re[k].number++;

}

}

output(re);

return(1);

}

void output(struct stat *p)

{ if(p->length==(p+1)->length)

printf("the length of 2 strings is equal.\n");

else

printf("the length of 2 strings is different.\n");

if(p->blank==(p+1)->blank)

printf("the amounts of blanks in 2 strings is equal.\n");

else

printf("the amounts of blanks in 2 strings is different.\n");

if(p->letter==(p+1)->letter)

printf("the amounts of letters in 2 strings is equal.\n");

else

printf("the amounts of letters in 2 strings is different.\n");

if((*p).number==(p+1)->number)

printf("the amounts of numbers in 2 strings is equal.\n");

else

printf("the amounts of numbers in 2 strings is different.\n");

}

第10章

1、C文件的特点是：C系统在处理文件时，并不区分类型，都看成是字符流，按字节进行处理。输入输出字符流的开始和结束只由程序控制而不受物理符号(如回车符)的控制。因此C语言文件也叫流式文件。流式文件准许对一个字符进行存取, 这增加了数据处理的灵活性。

缓冲文件系统：缓冲文件系统自动在内存区开辟一个确定大小的缓冲区，使数据输入输出都先通过缓冲区。

非缓冲文件系统：非缓冲文件系统不自动开辟确定大小的缓冲区，而是由程序员为每个文件设定一个缓冲区。

2、文件类型指针是缓冲文件系统的一个重要概念。文件类型指针是指向描述文件信息结构体的结构体变量，用于文件操作。在C语言中，对普通数据文件的所有操作都必须依靠文件类型指针来完成。要想对文件进行操作，首先必须将想要操作的数据文件与文件指针建立联系，然后通过这些文件指针来操作相应的文件。

3、打开文件，是建立文件的各种有关信息，并使文件指针指向该文件，以便进行其它操作。

关闭文件则断开指针与文件之间的联系，也就禁止再对该文件进行操作。

4、C语言程序中，文件操作顺序为：打开－读/写－关闭。

5、

#include <>

#define NULL 0

main()

{

FILE *fp;

char ch;

int linenum,chnum,i=0,l=0;

fp=fopen("","r");

if(fp==NULL)

{

printf("File can't be opened.\n");

exit(1);

}

ch=fgetc(fp);

linenum=0;

chnum=0;

while(ch!=EOF)

{

while(ch!='\n')

{

chnum++;

ch=fgetc(fp);

}

linenum++;

if (i

{

i=chnum;

l=linenum;

chnum=0;

}

ch=fgetc(fp);

}

printf("\nthe longest line is the %d line,and there are %d characters.",l,i);

fclose(fp);

}

第11章

1、

#include <>

#include <>

#define NULL 0

typedef int ElemType;

typedef struct LNode{

ElemType data;

struct LNode *next;

}LNode,*LinkList;

LNode* create_LinkList(int n)/*创建链表*/ {

LNode *s,*head,*L;

ElemType x;

int k=0;

L=(LNode *)malloc(sizeof(LNode));

if(L==0)

{

printf("error!");

exit(1);

}

else

{

L->next=NULL;

}

head=L;

while(k

{

scanf("%d",&x);

s=(LNode *)malloc(sizeof(LNode));

if(s==0)

{

printf("error!");

exit(1);

}

s->data=x;

s->next=NULL;

L->next=s;

L=s;

k++;

}

return (head);

}

void print_LinkList(LinkList L)/*输出链表*/ {

LNode *h;

h=L;

while(h->next!=NULL)

{

printf(" %d ",h->next->data);

h=h->next;

}

}

int num_LinkList(LinkList L)

{

int i=0;

while(L->next!=0)

{

i++;

L=L->next;

}

return i;

}

LNode* Insert(LinkList L,ElemType x)

{

int k,i;

LNode *s,*z,*l;

s=L->next;

k=num_LinkList(L);

for(i=0;i

if(s->data

{l=s;

s=s->next;

}

else break;

z=(LNode *)malloc(sizeof(LNode));

if(z==0)

{

printf("error!");

exit(1);

}

z->data=x;

if(s==NULL) {l->next=z;z->next=NULL;}

else

if(i==0)