大学C语言课本课后习题相应答案及详细解答

5-1

#include"stdio.h" void main()

{

char c1,c2;

printf("c1:");

c1=getchar();

if(c1>='a'&&c1<='z') c2=c1-32;

else if(c1>='A'&&c1<='Z') c2=c1+32;

else c2=c1;

printf("=>%c\n",c2);

}

5-2

#include"stdio.h"

void main()

{

char c;

printf("c:");

c=getchar();

if(c>='A'&&c<='Z')

if(c=='A') printf("没有前面的字母！");

else if(c=='Z') printf("没有后面的字母!!");

else printf("前面的字母=%c,后面的字母=%c",c-1,c+1);

printf("\n");

} 5-3

#include"stdio.h"

void main()

{

int s;

char g;

printf("s:");

scanf("%d",&s);

if(s>=0&&s<=100){

switch(s/10){

case 9:

case 10: g='A';break;

case 8: g='B';break;

case 7: g='C';break;

case 6: g='D';break;

default: g='E';

}

printf("g=%c\n",g);

}

else printf("成绩不在百分制范围内！\n"); }

5-4

#include"stdio.h"

void main()

{

int y,m,d,dok;

int yy,mm,dd;

printf("y,m,d:");

scanf("%d,%d,%d",&y,&m,&d);

switch(m){

case 1: case 3: case 5: case 7: case 8: case 10: case 12:

if(d>0&&d<=31) dok=4;

else dok=0;

break;

case 4: case 6: case 9: case 11:

if(d>0&&d<=30) dok=3;

else dok=0;

break;

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

if(d>0&&d<=29)

dok=2;

else dok=0;

else

if(d>0&&d<=28)

dok=1;

else dok=0;

break;

default: dok=0;

}

if(dok==0) printf("月份或日期不对！\n");

else{

switch(dok){

case 1: if(d==28){yy=y;dd=1;mm=m+1;}

else{yy=y;dd=d+1;mm=m;}

break;

case

2:if(d==29){yy=y;dd=1;mm=m+1;}

else{yy=y;dd=d+1;mm=m;}

break;

case

3:if(d==30){yy=y;dd=1;mm=m+1;}

else{yy=y;dd=d+1;mm=m;}

break;

case 4:if(d==31)

if(m==12){yy=y+1;dd=1;mm=1;}

else

{yy=y;dd=1;mm=m+1;}

else{yy=y;dd=d+1;mm=m;}

break;

}

printf("Tomorrow:%d年%d月%d日\n",yy,mm,dd);

}

}

5-5

#include"stdio.h"

void main()

{

int a,b,c,t;

printf("a,b,c:");

scanf("%d,%d,%d",&a,&b,&c);

if(a+b>c&&b+c>a&&a+c>b){

if(a>b){t=a;a=b;b=t;}

if(a>c){t=a;a=c;c=t;}

if(b>c){t=b;b=c;c=t;}

if(a==b&&b==c) printf("等边三角形.");

else if(a==b||b==c||a==c) printf("等腰角形.");

else if(c*c==a*a+b*b) printf("直角三角形.");

else printf("任意三角形.");

printf("\n");

}

else printf("不能构成三角形！\n");

}

6-1

#include"stdio.h"

void main()

{

int a,b,m,n,k;

printf("m,n:");

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

a=m;

b=n;

k=a%b;

while(k){

a=b;

b=k;

k=a%b;

}

printf("%d\n",(m*n/b));

}

6-2

#include"stdio.h"

void main()

{

int n;

int i,j,s;

printf("n=");

scanf("%d",&n);

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

s=0;

for(j=1;j

if(i%j==0) s=s+j;

if(s==i) {

printf("%d:",i);

for(j=1;j

if(i%j==0) printf("%d ",j);

printf("\n");

}

}

} 6-3

#include"stdio.h"

#include"math.h"

void main()

{

double x,y,zd,zx,x1,x2;

zd=zx=50;

for(x=0;x<=2;x=x+0.2){

y=2*pow(x,3)-3*pow(x,4)+6*pow(x,5)-4*x+50;

if(y>zd){ zd=y;x1=x;}

if(y

}

printf("x=%f,max=%f\n",x1,zd);

printf("x=%f,min=%f\n",x2,zx);

}

6-4

#include"stdio.h"

void main()

{

double x,sum=0,a,b,c;

int i;

printf("x=");

scanf("%lf",&x);

a=x;

b=1.0;

c=1.0;

for(i=1;i<=10;i++){

sum=sum+a/(b*c);

a=a*x*x;

b=b+2;

c=c*i;

}

printf("y(%.2lf)=%lf\n",x,sum);

}