c primer plus 习题答案(1)

 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 #define SIZE 30
 4 int main(void)
 5 {
 6     int o_num=0, e_num=0; 
 7     int i, j; 
 8     int num[SIZE];
 9     printf("please input number\n");
10     scanf("%d", &num[i]);
11     j=0;
12 
13     for(i=0;num[i++]!=0;)
14     {
15         if(num[i]%2==0)
16         {
17             j++;
18             e_num+=num[i];
19         }
20         else
21             o_num+=num[i];
22     }
23     printf("%d %d", j, e_num/j);
24     printf("%d %d", i-j, o_num/(i+1-j));
25 
26     system("pause");
27     return 0;
28 }

 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 
 4 int main(void)
 5 {
 6     int num=0;
 7     char ch;
 8 
 9     while(1)
10     {
11         if((ch=getchar())==‘#‘)
12             break;
13         if(ch==‘e‘&&(ch=getchar())==‘i‘)
14             num++;
15         else if(ch==‘#‘)
16             break;
17     }
18 
19     printf("%d", num);
20 
21     system("pause");
22     return 0;
23 }

 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 
 4 int main(void)
 5 {
 6     int num=0;
 7     char ch;
 8 
 9     while(1)
10     {
11         if((ch=getchar())==‘#‘)
12             break;
13         else if(ch==‘e‘)
14         {
15             switch(ch=getchar())
16         {
17                 case ‘i‘: num++;
18                 case ‘#‘: break;}
19         if(ch==‘#‘)
20             break;}
21         if(ch==‘#‘)
22         break;
23     }
24 
25     printf("%d", num);
26 
27     system("pause");
28     return 0;
29 }

 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 int get_int(void);
 4 #define BASETIME 40
 5 #define RATE1 0.15
 6 #define RATE2 0.2
 7 #define RATE3 0.25
 8 
 9 
10 int main(void)
11 {
12     float time, gross, net_income, tax, payrate, i;
13 
14     for(i=1;i<=48;i++)
15         printf("*");
16     printf("\n");
17     printf("Enter the number correspongding to the desired pay rate or action:\n");
18     printf("1)$%-.2f/hr%18c 2)$%-.2f/hr%18c\n", 8.75, ‘ ‘,9.33,‘ ‘);
19     printf("3)$%-.2f/hr%18c4)$%-.2f/hr%18c\n", 10.00, ‘ ‘,11.20,‘ ‘);
20     printf("5)quit");
21     printf("\n");
22     for(i=1;i<=48;i++)
23         printf("*");
24     printf("\n");
25 
26     while(1)
27     {
28     printf("Please enter your pay rate.\n");
29     switch(get_int())
30     {        
31         case 1: payrate=8.75;
32                 break;
33         case 2: payrate=9.33;
34                 break;
35         case 3: payrate=10.00;
36                 break;
37         case 4: payrate=11.20;
38                 break;
39         case 5: break;             
40     }
41     if(get_int()==5)
42         break;
43     printf("Please enter your working hours.\n");
44     while(scanf("%f", &time)==1)
45     {
46         if(time<=40)
47             if(time<=30)
48                 printf("the gross/tax/net_income is %f %f %f",time*payrate, time*payrate*RATE1, time*payrate-time*payrate*RATE1);
49             else
50                 printf("the gross/tax/net_income is %f %f %f",300+(time-30)*payrate, 300*RATE1+(time-30)*payrate*RATE2, (300+(time-30)*payrate)-(300*RATE1+(time-30)*payrate*RATE2));
51         else if(time>40)
52             printf("the gross/tax/net_income is %f %f %f",450+(time-40)*1.5*payrate, 300*RATE1+150*RATE2+(time-40)*1.5*payrate*RATE3, 450+(time-40)*1.5*payrate-300*RATE1-150*RATE2-(time-40)*1.5*payrate*RATE3);
53         printf("\n");
54         printf("enter q to quit.\n");
55     }
56     }    
57 
58     system("pause");
59     return 0;
60 }
61 
62 
63 int get_int(void)
64 {
65     int num;
66 
67         scanf("%d", &num);
68         switch(num)
69         {
70         case 1: return num;
71                 break;
72         case 2: return num;
73                 break;
74         case 3: return num;
75                 break;
76         case 4: return num;
77                 break;
78         case 5: return num;
79                 break;
80         default:
81             printf("Please input an integer range from 1~5\n");
82         }
83 }

 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 int get_char();
 4 
 5 int main(void)
 6 {
 7     int bill;
 8     double tax;
 9 
10     while(1)
11     {
12         printf("Please input your taxable income.\n");
13         printf("enter q to quit.\n");
14         if(scanf("%d",&bill)!=‘1‘)
15             break;
16         switch(get_char())
17         {
18         case ‘1‘: if(bill<=17850)
19                       tax=0.15*bill;
20                   else
21                       tax=17850*0.15+(bill-17850)*0.28;
22             printf("The tax is %f\n", tax);
23             break;
24         case ‘2‘: if(bill<=23900)
25                       tax=0.15*bill;
26                   else
27                       tax=23900*0.15+(bill-23900)*0.28;
28             printf("The tax is %f\n", tax);
29             break;
30         case ‘3‘: if(bill<=29750)
31                       tax=0.15*bill;
32                   else
33                       tax=29750*0.15+(bill-29750)*0.28;
34             printf("The tax is %f\n",tax);
35             break;
36         case ‘4‘: if(bill<=14875)
37                       tax=bill*0.15;
38                   else
39                       tax=14875*0.15+(bill-14875)*0.28;
40             printf("The tax is %f\n",tax);
41             break;
42         }
43     }
44     system("pause");
45     return 0;
46 }
47 
48 int get_char()
49 {
50     int num;
51     printf("Please enter a number.\n");
52     
53     while(scanf("%d", &num))
54     if(num!=1&&num!=2&&num!=3&&num!=4)
55         printf("Please enter again.\n");
56     else    
57         return num;
58     
59 }