c primer plus 习题答案(2)
p242.8
1 #include<stdio.h>
2 #include<stdlib.h>
3
4 int main()
5 { 6 int x, y, z, num; 7 int largest(int a, int b, int c); 8 printf("please enter three numbers."); 9 printf("enter q to quit.\n"); 10 while(scanf("%d%d%d",&x, &y, &z)==3) 11 { 12 num=largest(x, y, z); 13 printf("the largest number is %d\n", num); 14 printf("please enter three numbers."); 15 printf("enter q to quit.\n"); 16 } 17 18 system("pause"); 19 return 0; 20 } 21 22 int largest(int a, int b, int c) 23 { 24 if(a>b) 25 { 26 if(a>c) 27 return a; 28 else return c; 29 } 30 else 31 { 32 if(b>c) 33 return b; 34 else return c; 35 } 36 }
p242.9
1 #include<stdio.h>
2 #include<stdlib.h>
3
4 int main()
5 { 6 int num; 7 printf("Please choose one of the following:\n"); 8 printf("1) copy files 2) move files\n"); 9 printf("3) remove files 4) quit\n"); 10 printf("Enter the number of your choice:\n"); 11 scanf("%d", &num); 12 while(num>=1&&num<=4) 13 { 14 if(num==4) 15 { 16 printf("quit\n"); 17 break; 18 } 19 switch(num) 20 { 21 case 1: printf("copy files"); 22 break; 23 case 2: printf("move files"); 24 break; 25 case 3: printf("remove files"); 26 break; 27 default:printf("please input number only from 1~4"); 28 } 29 printf("\n"); 30 printf("Enter the number of your choice:\n"); 31 scanf("%d", &num); 32 } 33 34 35 system("pause"); 36 return 0; 37 }
p243.5
1 #include<stdio.h>
2 #include<stdlib.h>
3 void larger_of(double *, double *);
4
5 int main(void) 6 { 7 double x, y; 8 scanf("%lf%lf", &x, &y); 9 printf("x is %lf y is %lf.\n", x, y); 10 larger_of(&x, &y); 11 printf("Now x is %lf y is %lf.\n", x, y); 12 system("pause"); 13 return 0; 14 } 15 16 void larger_of(double *x, double *y) 17 { 18 if(*x>*y) 19 *y=*x; 20 else *x=*y; 21 }
p243.6
1 #include<stdio.h>
2 #include<stdlib.h>
3 int get_ch(int);
4
5 int main(void) 6 { 7 int ch, num; 8 while((ch=getchar())!='#') 9 { 10 num=get_ch(ch); 11 if(num>0) 12 printf("the char is a letter. number is %d\n", num); 13 else 14 printf("the char is not a letter.\n"); 15 } 16 17 system("pause"); 18 return 0; 19 } 20 21 int get_ch(int ch) 22 { 23 int i; 24 if(ch>='A'&&ch<='Z') 25 { 26 i=ch-'A'+1; 27 return i; 28 } 29 else if(ch>='a'&&ch<='z') 30 { 31 i=ch-'a'+1; 32 return i; 33 } 34 else return -1; 35 }
p243.7
1 #include<stdio.h>
2 #include<stdlib.h>
3 double power(double, int);
4
5 int main(void) 6 { 7 double n; 8 int exp; 9 printf("please enter a number and a exp.\n"); 10 while(scanf("%lf%d", &n, &exp)==2) 11 printf("%lf to the power %d is %lf\n", n, exp, power(n, exp)); 12 13 system("pause"); 14 return 0; 15 } 16 17 double power(double n, int p) 18 { 19 int i; 20 double pow=1; 21 22 if(n!=0,p>0) 23 { 24 for(i=1;i<=p;i++) 25 pow*=n; 26 return pow; 27 } 28 else if(n!=0,p<0) 29 { 30 for(i=1;i<=-p; i++) 31 pow*=n; 32 return 1.0/pow; 33 } 34 else if(n!=0,p=1) 35 return 1; 36 else if(n=0) 37 return 0; 38 }