1 #include <math.h>
 2 #include <stdio.h>
 3 
 4 int main() 
 5 {
 6      float a, b, c, x1, x2;
 7      float delta, real, imag;
 8      
 9      printf("Enter a, b, c: ");
10      
11      while(scanf("%f%f%f", &a, &b, &c) != EOF)
12 {
13      if(a == 0)
14      { printf("
 
not quadratic equation.\n\n"); }
15      else 
16      { delta = b*b - 4*a*c; }
17      
18      if(delta >= 0)
19      {
20      x1 = (-b + sqrt(delta)) / (2*a);
21      x2 = (-b - sqrt(delta)) / (2*a);
22      printf("x1 = %.2f, x2 = %.2f\n\n", x1, x2);
23      }
24      else 
25      {
26      real = -b/(2
 
*a);
27      imag = sqrt(-delta) / (2*a);
28      printf("x1 = %.2f + %.2fi, x2 = %.2f - %.2fi\n\n", real,imag,real,imag);
29      }
30      
31      printf("Enter a, b, c: ");
32 }
33 
34 return 0;
35 }

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <time.h>
 4 #define N 5
 5
 
 int main() {
 6 int x, n;
 7 
 8 srand(time(0)); // 以當前系統時間作為隨機種子
 9 n = 0;
10 
11 do {
12    n++;
13    x = rand()%10; // 生成一個0~9之間的隨機整數
14    printf("%3d", x);
15    }while(n<N);
16 
17    printf("\n");
18    
19    return 0;
20 }

 1 #include <stdio.h>
 2 #include <math.h>
 3 
 4 int main()
 5 {
 6     int n=100,a=0,m=2;
 7     
 8     while(n<200)
 9     {
10         while(m <=sqrt(n))
11         {
12             if(n%m!=0)
13             {m+=1;}
14             else
15             {break;}
16         }
17         if(m>sqrt(n))
18         {
19             printf("%d\n",n);
20             a+=1;
21         }
22         n+=1;
23         m=2;
24     }
25     printf("個數為%d",a);
26     
27     return 0; 
28 }

 1 #include <stdio.h>
 2 #include <math.h>
 3 
 4 int main()
 5 {
 6     int a,b,c,sum=0,n=0;
 7     
 8     while(scanf("%d",&a) != EOF)
 9 {
10     
11     while(a>0)
12     {
13         b=a%10;
14         a/=10;
15         if(b==1||b%2==1)
16         {
17         c=b*pow(10,n);
18         n+=1;
19         sum+=c;
20         }
21     }
22     printf("%d\n",sum);
23     printf("\n");
24     sum=0;
25     n=0;
26 }
27     
28     return 0;
29 } 

 1 #include <stdio.h>
 2 #include <math.h>
 3 
 4 int f(int);
 5 int f(int k)
 6 {
 7     int m=k;
 8 
 9     if (k > 1)
10     {
11         while (k > 1)
12         {
13             m = m* (k - 1);
14             k = k - 1;
15         }
16     }
17     else
18         m = 1;
19 
20 
21     return m;
22 }
23 
24 
25 int main()
26 {
27     int n,x;
28     double a = 1,sum=0;
29     
30     while (scanf("%d", &n)!=EOF)
31     {
32         if (n < 1 || n>10)
33         {
34             printf("請輸入1到10間的數字");
35         }
36         else
37         {
38             while (n > 0)
39             {
40                 x = f(n);
41                 sum += a / x * pow(-1, n - 1);
42                 n = n - 1;
43             }
44         }
45 
46         printf("%lf\n", sum);
47         printf("\n") ;
48         a = 1;
49         sum = 0;
50     }
51 
52 
53         return 0;
54 }

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 
 4 int main()
 5 {
 6     int a,b,k=1;
 7     a=rand()%32;
 8     
 9     while(k<4)
10     {
11         scanf("%d",&b);
12         k+=1;
13         
14         if(b==a)
15         {
16             printf("猜對了\n");
17             break; 
18         }
19         else if(b<a)
20         {printf("猜小了\n");}
21         else
22         {printf("猜大了\n");} 
23     }
24     
25     if(k==4)
26     {printf("次數用完，答案為%d",a);}
27     else
28     {printf("猜對了，答案為%d",a);}
29     
30     return 0; 
31 }